All four of the Madison Square Gardens have produced great lore, but tonight's Sugar Ray Leonard-Terry Norris bout promises to be just another line in the tomes of New York boxing history unless Leonard has made a terrible miscalculation. A Norris upset would go down as a chapter all its own.

Leonard is a 12-5 favorite to dethrone the World Boxing Council junior middleweight champion in a meeting that can be explained only by saying that some mysterious demons must prod Leonard to keep at his risky craft when all logic says he's reached a time to sit back and enjoy the riches of a boxing lifetime.

Leonard (36-1-1), who will turn 35 on May 17, is taking on the 23-year-old Norris (26-3) at a scheduled 12 rounds (Showtime, 10 p.m.) with the stated intention of "testing" himself against a fast, younger fighter. By dropping to the 154-pound limit (he weighed in yesterday at an exact 154), Leonard is thought to be looking beyond Norris (152 1/2) to something of greater import, perhaps a showdown with the dynamic Julio Cesar Chavez (73-0), who is seven to 10 pounds lighter than Leonard.

If Leonard fighting at 154 sounds familiar, it is. He's going over old, old ground. He stopped Ayub Kalule in the ninth round for the World Boxing Association junior middleweight title as long ago as June 25, 1981. In 1987, he weighed 160 when he came out of retirement to upset Marvelous Marvin Hagler. Leonard's lawyer Mike Trainer declared that Leonard had grown into a middleweight. Now Trainer says that 154 has always been Leonard's best weight.

But neither his weight, nor the opponent, nor the historic setting -- nothing has sparked interest in this fight. Norris is little known and hand-picked by Leonard. The only thing that can be said in Norris's favor is that Leonard's last two little-known, hand-picked opponents -- Kevin Howard and Donny Lalonde -- both knocked him down in the fourth round before being knocked out themselves in the ninth round.

"I'm surprised Leonard is taking me on," Norris said this week. "He needed someone who was going to help him prove himself. Beating me would prove he's not losing anything. It's a test. He just took the wrong test."

Norris, a counterpuncher, has performed solidly in his last two outings. He knocked out John "The Beast" Mugabi in the first round to win his title last March 31 in Tampa, then in his one defense scored a 12-round decision over Rene Jacquot July 13 in France.

But before that, Norris tried to win the WBA 154-pound title in Atlantic City, only to be knocked out by the hard-punching Julian Jackson. In a torrid first round, Norris looked to be an easy winner but reality put him down hard in round two. "I got a little too cocky," said Norris, who was raised in Lubbock, Tex., and trains in Campo, Calif., near San Diego. "He caught me with a good shot. It was a lesson. I rebounded and I'm a champion."