After today's extraordinary program at Gulfstream Park, racing fans should know who the best Derby-age colts in America are -- if, indeed, there are any good ones.

Stephan's Odyssey, Proud Truth and Banner Bob head a field of 11 in the $300,000 Florida Derby (5 p.m., WJZ-TV-13), the most important 3-year-old stake of the year to date. A half-hour earlier, the defending champion of this generation, Chief's Crown, will make his season debut in the seven-furlong Swale Stakes. And in an allowance race, the highly promising colt Rhoman Rule makes his first start of the year.

With no 3-year-olds of distinction in California, New York or Arkansas, it is likely that the colts based in Florida are the cream of this crop. Yet despite the hype here for the favorites in the Florida Derby, Proud Truth and Stephan's Odyssey, they haven't given any performances that are as good as their press notices.

Both colts have good breeding, come from fancy stables and have stretch- running styles that make them look like glittery Derby candidates. But when they rallied to finish one-two in the Fountain of Youth stakes, they were running down exhausted speed horses and their final time was decidedly mediocre.

Stephan's Odyssey does figure to improve off that performance and reverse his photo-finish loss to Proud Truth. The Fountain of Youth was his first start of the winter, and he was giving his rival a 10-pound weight concession. But it still is questionable whether he can beat Banner Bob in the Florida Derby. Banner Bob gave the one impressive performance by a 3-year-old this winter when he won the seven-furlong Hutcheson Stakes in 1:21 3/5.

"This colt's never done anything wrong," trainer Buddy Sarner said. "It's a question of how far he'll go." Under other circumstances, it would be doubtful whether Banner Bob could go the 1 1/8 miles of the Florida Derby; he has never won beyond a mile. But every other contender in the field is a stretch-runner; Banner Bob should be able to dictate the pace and open as big a lead as jockey Keith Allen wants.

Handicappers can at least deal rationally with the key issues in the Florida Derby, but the debut of Chief's Crown in the Swale Stakes is shrouded with uncertainty. The best 2-year-old in America last year, Chief's Crown has trained unimpressively for most of the winter, except for one day this week when he worked six furlongs in 1:12.

"On that day," said clocker Jim Milner, "he came out onto the track looking like a new horse. He was a monster." So it is hard to assess just how fit and sharp Chief's Crown is, although if he is a semblance of his old self he should have no trouble beating his undistinguished rivals. The quality of his performance, however, should indicate whether the colt still deserves to be considered the leader of his generation.

In the first race at Gulfstream Park, Rhoman Rule will face a decent allowance field at seven furlongs. His third-place finish in last fall's Laurel Futurity was one of the most impressive performances by a 2-year-old last season, and he could gain credibility as a Kentucky Derby contender if he runs well today. But then, this looks like a year when any 3-year-old who shows a flash of ability will merit consideration as a Derby contender.