For a guy going on 45, David Leslie is in great shape. He works out a lot, and trains regularly at Gleason’s.

Which is just as well. Because this Thursday night he climbs into a boxing ring with Gerry Cooney for what he hopes will be a four-round exhibition match. It will be the main event of an extravaganza he calls Box Opera 3 (www.boxopera3.com). In spirit it’ll be as much like professional wrestling as professional boxing, with a lot of performance art (including lifesize Rock’em Sock’em Robots and a reenactment of Lincoln’s assassination) and some topless women thrown in.

David Leslie is the "Impact Addict," a performance artist as stunt man. His stunt career began in the mid-80s, when he was a sculptor approaching his 30s, doing odd pieces like a portrait of Johnny Unitas. He says he began to feel like "I’m the guy at the Super Bowl souvenir stand selling the little tchotchkes that reference the action on the field." He decided he wanted to be the action. "My struggle was, I’m going into my 30s. I’m supposed to be acting like a grown man, and it’s like I’m going back to Little League Football."

But he went ahead anyway with his first stunt, an Evel Knievel-style "rocket jump" over 1000 watermelons in ’86. "And then I was hooked." Next, in one of his most visually stunning acts, he jumped off a three-story building on Ave. B in a suit of bubble-wrap and lightbulbs, earning the title "Impact Addict." In other shows he fought six kung-fu fighters simultaneously; celebrated Chinese New Year by blowing himself up in a costume made of firecrackers; fought an exhibition match with Riddick Bowe on the Staten Island ferry; and in 1989 he threw himself off the roof of P.S. 122 in an 80-foot freefall dressed up as Maria von Trapp.

He says that was the closest he’s come to really hurting himself, when he went through his landing gear and "my body punched a hole in the three-quarter-inch plywood platform... I’ve always said Mark Russell, the director of P.S. 122, has got to be more crazy than I am" for letting him do it. After all, if the stunt had gone really wrong, Russell could have gone to jail. Leslie would simply have been dead. "Dead in drag," he jokes.

Why did he do it? The adrenaline? Is he a masochist?

"I’m a showman," he replies. On one level, the idea is to get hipster art audiences to look at "lowbrow spectacle" like stunts or boxing in a new way. Also, he says, "For me, there are two shows going on. There’s the one that you guys in the audience are seeing, and the one that I’m seeing when I’m on top of P.S. 122. I’ve got a whole other show. Nobody gets to see that but me, and that blows my mind. That’s the addict part of me. My addiction is not to have a bunch of people watch me do something. It’s standing there going, ‘Fuck, I have to go. There’s 1000 people down there and I’ve gotta go.’

"I love being in a situation where I should be getting hurt, where I could certainly die, and don’t get hurt," he elaborates. "If I get hurt, it’s a failure. I’m embarrassed. I look like an idiot. And you feel stupid because you watched it."

After the P.S. 122 show Leslie was offered various showbiz opportunities: opening for the Stones, an early version of MTV’s Jackass. Instead he retired the Impact Addict and pursued a quieter, more grownup career for the next 11 years as the performance-art curator at the Kitchen, "where I was fairly miserable for two years," and then as a casting director.

In 2000 he met then New York Press columnist Jonathan Ames and the two goaded each other into the ring for the first Box Opera. The Impact Addict was back. Older, but no less ballsy. Both guys trained seriously in the months leading up to the fight, wherein Leslie pretty much kicked Ames’ ass. Leslie fought another arty type in Box Opera 2, and then there was the knockout contest, where he challenged all comers in the audience to deck him and win $1000. That night ended in a small riot, with Leslie still standing and keeping his dough. "I can take a hit," he says.

One hopes so. For Cooney, this fight is a way to raise money and awareness for FIST, the charity for current and retired boxers. For Leslie, it’s a way to kick the Box Opera spectacle up to another level.

"I’ve been to see Cooney fight four times in the past year, starting with an exhibition fundraiser for the Twin Towers Fund. He’s only a year older than me–next month I’ll be 45, he’ll be 46. He’s in great shape. Nobody could touch him. He’s fast. You’ll be shocked at how quick his jab is. Very smart, very fast, and doesn’t let people touch him. He’s like, ‘We’ll go out there and I’ll beat you up and you’re not going to touch me. And if you try to touch me, I’m gonna punish you.’

"I don’t want to go out there with somebody who’s just going to toy around," he continues. "He could literally kill me if he wants. I’m gonna go out there and piss him off, and he’s gonna punish me, and that’s what the crowd is going to see. I’m going to be trying as hard as I can to get under or around his incredibly fast jab and really rattle him, get him to where he’s like, ‘I’ve got to get this asshole off of me.’"

A friend recently told Leslie that Box Opera is "like an over-produced, very public midlife crisis. That’s probably right. But I’m having a damn good time doing it."

For his next extravaganza, he’s plotting a return to his Knievel roots: he wants to "jump a motorcycle from Brooklyn to Manhattan" across the East River. He acknowledges the extreme potential for failure. "I’ll put it this way," he grins. "There’ll be a receiving ramp on one side, and a take-off ramp on the other, and I don’t know how much use the receiving one will get."