When most people hear the name Elvis Costello, they think of a nerdy-looking guy with knock-knees and Buddy Holly glasses. The bratty poet-king of punk rock. The critics' darling who gets zero airplay. That English twerp with the big mouth who slandered Ray Charles during a bar brawl in Columbus, Ohio, in 1979.

By last year, Costello realized something had to be done about this little identity problem. Why, even the shock value of casually assuming the most sacred name in rock & roll had worn off. Now only the damage remained. So Elvis Costello decided it was time to be plain old Declan Patrick MacManus again.

"I was tired of the way people saw Elvis Costello: they saw this funny pair of glasses and a load of mannerisms, and they had all these preconceived ideas of what I was and who I was," he complains between gulps of Perrier water in his Manhattan hotel room. "I started to think of it as a bit of a curse. I started to wonder if there were people who were not listening to my records simply because they associated me with 1978 or '79. Elvis Costello was becoming a brand name, kind of like Durex." Durex, he adds with a wink, is the name of a popular English prophylactic.

So now, a decade after his rechristening by his flamboyant manager, Jake Riviera, the former Declan MacManus is soon to become the former Elvis Costello. His new album,'King of America, is credited simply to the Costello Show, although his American record company, Columbia, politely insisted that "Featuring Elvis Costello" be added in parentheses as commercial insurance. His thirteen original songs on the record are credited to MacManus. And his coproduction credit is Declan Patrick Aloysius MacManus (the name Aloysius is a whimsical addition inspired by a deceased British comedian).

Costello has already legally reverted to his original, weighty, Irish-flavored name, although his current passport still reads, "Elvis Costello" - but not for long. "My passport's about to run out," he explains, "so I'll have to change it back. But then I'll have to have 'known as' on it. If you have a recognizable face, they think you're trying to pull a fast one."

This is no fast one. The shedding of his Elvis skin is only the most visible evidence of Costello's concentrated re-examination and wholesale transformation of his image, his art and his private life. He is soon to wed Cait O'Riordan, a bassist and singer with the U.K. folk-punk outfit the Pogues. The nuptials are being held up by the ongoing divorce proceedings between Costello and his wife, Mary. The two were married in 1974 and have an eleven-year-old son, Mark, but theirs was a marriage rocked at times by the pressures of Costello's fame and, in 1979, by his widely public fling with rock-star girlfriend Bebe Buell.

When Costello temporarily dropped from sight last year after doing a series of solo tours with his friend T-Bone Burnett as opening act, the British press speculated that he was suffering from divorce trauma, alcoholism and songwriter's block. In fact, he was vigorously courting O'Riordan (the two even wrote a song together, ''Lovable," which appears on King of America). Costello first saw the Pogues at a London show in the summer of 1984, and he was immediately taken with their lively, rather alcoholic approach to Celtic folk music. Before long, Costello was producing the Pogues' second LP, Rum Sodomy & the Lash, which became a U.K. best seller; he was also in love with O'Riordan.

In the meantime, Costello submitted three numbers for the soundtrack of Absolute Beginners, Julien Temple's film adaptation of Colin MacInnes' classic British novel of Fifties youth angst. (According to Elvis, the tunes didn't make the final cut because of the film's budget problems.) He was also writing songs for his next LP at a ferocious clip. With Burnett acting as editor, conscience and unabashed fan, Costello then dissected each song, sometimes harshly, nixing overly slick metaphors and glib vocal performances. "We had to remind ourselves how good the good songs were," Costello says. "That means taking up only as much space as you can handle. If you know what you're singing about and really, really mean it, you can appear as large as life."

"We had one long conversation where we talked about who actually wrote good songs," remembers Burnett, a veteran of Bob Dylan's Rolling Thunder Revue who first worked with Costello on his 1984 solo tour of America "We started with 'Night & Day,' the Cole Porter song, and then we'd look at the Beatles and Bob Dylan - how many songs did they write as good as that? We were trying to sort out what we can expect from ourselves as writers."

When he recorded his new songs in Los Angeles last summer, Costello demanded from his rotating cast of U.S. sessionmen only the most basic accompaniment - the wispy brushwork of legendary New Orleans drummer Earl Palmer, the hip bass slap of jazz great Ray Brown and the pithy country clucking of guitarist James Burton, a former Elvis Presley sideman. The result on King of America is like Imperial Bedroom without amplifiers, a reductionist experiment in ambitious pop songwriting and a demonstration of his faith in the verities of simple, unadorned rock & roll. It's also Costello's first album since My Aim Is True without his regular backup band, the Attractions (they play on only one song, "Suit of Lights").

"It seems crazy to me that a record with such solid sounds on it could be regarded as unconventional," he grumbles. "But it has acoustic bass, mostly brushes, hardly any electric guitar and no synthesizers. It's all voice and all songs. No fancy arrangements, no all-star guest performances. It's not the soundtrack of a movie, I'm not on heroin, and I don't have AIDS. So," he concludes with an ironic grin, "I have no chance of having a hit."

Nevertheless, Costello is lobbying hard on behalf of the record. He has called a truce in his on-again, off-again war with the press, doing extensive interviews and even radio promotion for King of America. In New York recently, he appeared on a breakfast radio broadcast from a downtown club, taking questions from the audience and spontaneously erupting into a stormy live performance of his new single, a vivid, bluesy remake of the Animals' 1965 hit "Don't Let Me Be Misunderstood." In late 1977, he arrived stateside with a suitcase full of attitude. This time around, Costello is more smiles than scowls. He welcomes reporters into his hotel room with a hearty handshake, a cheery hello and an unexpectedly warm smile.

"The nonmusic press that covered me when I first came over, like Newsweek and Time, were very gorping," he claims. "They hadn't managed to talk to the Sex Pistols, and I was the next thing. I was the tame punk that could actually speak and didn't spit. But I was actually more obnoxious because of the very condescending way they treated me. As a result, it was defeating for both sides. They didn't get a good article, and I didn't get anything across that I wanted to say."

Costello recalls talking to his father, Ross MacManus, a big-band singer and cabaret performer, backstage at one of his first big London shows with the Attractions. "He said: 'I get the feeling they've come to see you die onstage or something, in some way to sacrifice yourself. There is something slightly morbid about it.' It was about that time that I started to realize the pitfalls. It started to worry me that my whole career was suddenly on a runaway course."

It was on his more recent solo tour, though, that Costello realized how much his fans actually thrived on his old negative energy. During the tour, Costello and Burnett cooked up a wacky encore act as the Coward Brothers, a boozy, wisecracking version of the Everly Brothers, in which they would mix absurd spontaneous banter with dismembered oldies like "San Francisco (Be Sure to Wear Flowers in Your Hair)" and straight country classics.

'We did the whole act as if we were on a reunion tour," Costello explains with a devilish chuckle, "and we talked as if we were doing all our old hits. But people didn't know what to make of it, particularly if I said anything funny. They'd be nervous of laughing in case I would come down and strangle them. People get this weird notion of what I'm about. They stop seeing me as a human being. I think they were almost a little upset that we were being so flippant. I sensed a couple of people in the audience that didn't like me making jokes, as if I'm supposed to be bitter. Isn't that ridiculous?"

Early last year, the Coward Brothers released a witty country-hoedown single in Britain called "The People's Limousine," based on their experiences touring Italy in a limo provided by a concert promoter who claimed to be a communist. For the Coward Brothers, the song was the beginning of a more serious artistic partnership, and by last June, Burnett was coproducing King of America.

Burnett believes that Costello does his best work when he isn't showing of£ ĞMy main criticism is that some of what he's done is too facile," Burnett says. "He has to be careful with his brain."

Costello agrees "I know how to write songs already. What I learned from T-Bone was when to leave them alone." He now dismisses his last two albums, 1983's Punch the Clock (which nearly went gold here) and 1984's Goodbye Cruel World (his worst-selling LP since the '81 Nashville experiment Almost Blue), as awkward Top Forty bids suffering from kitchen-sink production. Even the highly praised Imperial Bedroom - one of his three favorite works, along with This Year's Model and Get Happy - was too rococo for its own good, he says.

But there is more to Elvis Costello's conspicuous lack of U.S. chart success. Praised to the skies in the music press, Costello is in danger of becoming the New Wave Randy Newman, suspended in a kind of genius purgatory between the critics' good will and mainstream acceptance. "The carry-over of that argument," he says, laughing, "is that you critics might all be wrong. I might really be a charlatan."

Costello believes that King of America, with its acutely personal singing and heroically unfashionable acoustic sound, is more punk in spirit than most of the hardcore chain-saw rock he hears these days. "This is a punk record made by old people," he declares quite seriously. "But it's all a confrontation, isn't it? It's just that this is less obnoxious than the tactics we had before. We weren't always in the right, but we weren't always in the wrong, either. So there's no apology for what happened, except for the obviously idiotic things, where people got hurt or got the wrong idea of what happened." That, he adds, is a specific reference to the Columbus incident.

Nor does Costello offer any apology for his apparent inability to reap the success his reviewers have predicted for him since My Aim Is True, his first album. "If this record isn't a hit, then I'll make another one that is even more willful. I won't make the same record again." In fact, Costello plans to go back into the studio this spring, with the Attractions and his original producer, Nick Lowe. If he does go on the road this year, "it will be with a whole new repertoire. I will only play the songs I really like." He shows a hint of that old take-it-or-leave-it choler. "I won't be doing hits for the hell of it."