Who: Riddick Bowe (34-0, 29 KOs), Fort Washington, Md., vs. Evander Holyfield (29-1, 22 KOs), Atlanta What: For Bowe's International Boxing Federation and World Boxing Association heavyweight titles Where: Caesars Palace, Las Vegas When: Tomorrow. The main event will start approximately 11 p.m. EDT. Distance: 12 rounds Promoters: Spencer Promotions and Main Events, Inc., in conjunction with Caesars Palace TV: Pay per view begins at 9 p.m. Fight also can be seen at about 1,000 closed-circuit venues. Semi-windup: Thomas Hearns (50-4-1, 40 KOs), Detroit, vs. Andrew Maynard (21-5, 18 KOs) Laurel, light-heavyweights, 10 rounds