STALLONE'S HEAVY-DUTY TRANSITION; FOR `COP LAND' HE TAKES HEFT OVER HEFTY PAYCHECK.

Byline: Amy Dawes Daily News Film Writer

Twenty years later, Sylvester Stallone can still come across like a palooka with a heart. He did it in ``Rocky'' in 1977 and got an Oscar nomination for it, and he does it in ``Cop Land,'' a new movie in which he plays a slow-witted, paunchy New Jersey sheriff who idolizes the New York City cops from across the river.

And he's doing it now, in an interview in which he's explaining how nervous he is on the eve of the picture's release, and how humble he felt sharing scenes with the other stars - legitimate, big-name actors such as Robert De Niro, Harvey Keitel and Ray Liotta.

``This role is probably the most important thing I've ever done,'' said Stallone, his voice gentle and unassuming. ``Very rarely do you ever get an opportunity to redefine yourself. You make a mistake early on, and it's very hard to change people's opinion of you.

``And rightly so. So to get to go back and play a character like this ...'' He shakes his head. ``It seems parallel to what's actually happened to me. Because I'm the outsider. I'm never considered when it comes to serious filmmaking.

``I'd say this is the most important film I've ever done, because it's the one that shows if I have anything left.''

You might think Stallone is setting you up, trying to create the same kind of underdog backstory that made his breakthrough success with ``Rocky'' so satisfying to the public.

Then, he was a struggling actor who couldn't get a break, but who transformed himself by sheer tenacity into a hero - the writer and star of the movie that won the Oscar for Best Picture.

Now, he's one of the highest-paid actors in the industry, a $20 million action icon whose legacy includes a string of pictures in which his job, by his own admission, consisted of grunting, punching, shooting and collecting a paycheck.

Now he says he regrets all of that, and he wants another shot. And he's actually sweating while he's saying it.

``Look at me, I'm shvitzing!'' he says, fanning at his light blue shirt, which has sprung more leaks than a spaghetti strainer. ``It's like I have malaria!''

If he's acting, you've got to admit he's pretty good.

``When you're scared, it means you're doing something right,'' says James Mangold, the 33-year-old writer and director of ``Cop Land,'' whom Stallone, 51, refers to as ``the kid.''

``Sly said he wanted a challenge, he wanted an experience that was more than hitting a mark so a computer-generated boulder could come at him.''

Stallone's William Morris agent, Arnold Rifkin, called Mangold a year ago, wondering if he'd consider Stallone for the role of Freddy Heflin, a New Jersey sheriff who is deaf in one ear and is chosen as a kind of puppet law enforcement officer by the corrupt New York cops who make their home in a tiny riverside burg called Garrison.

Heart and soul

Without a doubt, Freddy is the heart and the hero of the movie, but it isn't the kind of role anyone has thought of Stallone for in a very long time. ``I couldn't imagine why he'd want to do it,'' said Mangold.

The movie's entire budget hardly equaled Stallone's customary quote. It was understood that the actor would work for a small fee - Mangold thinks it turned out to be around $50,000 - with profit points in the movie.

``I think it took tremendous courage for him to make that decision, but it was a real personal decision,'' said Mangold. ``He wanted to be inspired by making films again, to be alive again in the process.''

Harvey Weinstein, the co-chairman of Miramax, which financed the movie, was also in favor of Stallone playing the role, and urged Mangold to consider it.

Even before it came to winning over the public, Stallone said he had to deal with the attitudes of the other actors in the movie.

``I was actually very fearful, because I didn't know if I could Ncompete in their arena,'' he said, of a cast that also included Annabella Sciorra, Janeane Garafolo, and Cathy Moriarty. ``I sensed around the set that there was a kind of showdown coming. The day I had my first big scenes with De Niro, there were an awful lot of executives around.''

Actor Ray Liotta, who plays a high-strung cop named Figgis who serves as a catalyst for Freddy's moral transformation, admits that the other actors did have some concerns about Stallone. ``It wasn't really whether he could pull it off - I mean, we'd all seen `Rocky' - but whether he'd be willing to make the commitment,'' said Liotta. ``I mean, when your whole career has involved your physique, was he really going to gain the weight?''

The role of Freddy Heflin required Stallone, who's long been the No. 2 name in movie muscles after Arnold Schwarzenegger, to add about 40 pounds to his customary 170.

He said it's the hardest thing he's ever done.

Not the eating part. ``For that, you can't beat pancakes with peanut butter and cheesecake in the morning,'' says Stallone, with relish. ``Then you wash it down with chocolate milk.''

What killed him was swallowing his pride and making the mental adjustment.

``I didn't realize until three or four months into it what a man who looks like that feels like,'' he said. ``The loss of physical presence when you walk into a room. For 15 years, I'd been coming into a room chest first, making my statement that way. Suddenly, I had to rely on something else, maybe some intelligence or charm or politeness, to ingratiate myself with people.''

Line blurring

He may have made his living as an actor, an observer of what makes people tick, but Stallone says this as if it's a revelation. ``The line was starting to get blurred between myself and some of the roles I was playing,'' he says.

After a while, he started to let go of the ego he attached to his appearance. ``At first, I'd walk up to people and say, `I know I'm heavy, but this is not me. It's for a movieN. Got it?'

``Then I stopped making excuses. I took most of the mirrors out of the house. I just got into thinking about the performance,'' he says. ``With each pound that went on, there was a kind of heaviness, a lethargy, a world-weariness,'' he said. ``I started to feel like a real actor in that it became a pleasure to feel myself sinking into this character.''

``When I met with Sly, I sensed that if I could get the person he was showing to me on camera, without letting him develop any armor along the way, I would have something,'' said Mangold. ``Because he really is a tender-hearted man, and he does admit what he's nervous about.''

Mangold was taking something of a flier himself. He'd previously directed only one feature, a low-budget independent drama called ``Heavy.'' Now he was in charge of a movie with a cast that might have made a director such as Martin Scorsese or Quentin Tarantino envious.

Asked about his influences, Mangold names a musician instead - New Jersey bard Bruce Springsteen, who contributed two songs, ``Drive All Night'' and ``Stolen Car,'' to the movie's soundtrack.

``The stories Springsteen tells are very close to this movie,'' said Mangold, whose script was inspired by his own experiences growing up in a Hudson Valley town populated by cops and firemen. ``They're about people yearning to escape from their mistakes, to get out of a rut, to recapture the glory of their youth.''

It's a feeling that, believe it or not, Stallone can relate to. ``It was getting to where I just felt contempt when I looked back at some of the things I'd done,'' he said. ``I just accepted the money. There was no mental challenge.''

Mangold said that in accepting the role as Freddy, the artist formerly known as Rambo laid down some guidelines for casting the rest of the movie.

``He said he wanted to be part of an acting process and he wanted to work with the best. If he was going to give up his fee, he wanted to be in a situation where he was meeting eyes and exchangiNng energies with actors who could scare him.''

CAPTION(S):

3 Photos

Photo: (1--Cover--Color) BIG SHOTS

Stallone leads heavyweight cast in `Cop Land'

(2) ``This role is probably the most important thing I've ever done,'' says Sylvester Stallone, center, who co-stars with Robert De Niro, left, and Harvey Keitel in ``Cop Land.''

(3) Director James Mangold: ``When you're scared, it means you're doing something right.''