Three U.S. wrestlers captured silver medals at the respected Petrov Tournament of Greco-Roman wrestling in Pleven, Bulgaria, March 2-3.    The U.S. silver medalists were Jim Gruenwald (Colorado Springs, Colo./Sunkist Kids) at 60 kg/132 lbs.,  Mike Ellsworth (Colorado Springs, Colo./Michigan WC) at 66 kg/145.5 lbs.  and Dremiel Byers (Colorado Springs, Colo./U.S. Army) at 120 kg/264.5 lbs.    Gruenwald, who was sixth in the 2000 Olympics, won four of his five bouts. He won his pool competition, then defeated American Joe Warren in the quarterfinals, 5-0. His semifinal victim was Kalin Velinov of Bulgaria, in a 5-0 decision. He was beaten in the gold-medal finals by two-time Olympic champion Armen Nazarian of Bulgaria, 5-0.    Ellsworth also won four of his five matches, losing only in the gold medal finals to Alexander Sandev of Bulgaria, 4-0. He captured his pool with three wins, then pinned Nikolai Gergov of Bulgaria in the semifinals in 3:58.    Byers placed second in a four-man round-robin, winning two of his three bouts. He opened with a 4-2 overtime loss to 1996 Olympic bronze medalist Sergei Morieko of Bulgaria. Byers rebounded with a 7-2 win over Nikolai Iliev of Bulgaria, then a pin of Dimitat Tzachev of Bulgaria in 3:43.    A large team of American wrestlers participated in the tournament, and a number were able to place in the top 10 of their weight classes.    Placing fifth for the USA were Joe Espinoza (Marquette, Mich./USOEC) at 55 kg/121 lbs., Joe Warren (Colorado Springs, Colo./Michigan WC) at 60 kg/132 lbs. and Ethan Bosch (Colorado Springs, Colo./New York AC) at 84 kg/185 lbs.    Placing sixth were U.S. wrestlers T.C. Dantzler (Colorado Springs, Colo./New York AC) at 74 kg/163 lbs. and Jeff Funicello (Gilbert, Ariz./Sunkist Kids) at 84 kg/185 lbs.     2001 World Team member Keith Sieracki (Colorado Springs, Colo./U.S. Army) placed seventh at 74 kg/163 lbs. Taking eighth places were Mike Mathers (Marquette, Mich./USOEC) at 84 kg/185 lbs. and R.C. Johnson at 96 kg/211.45 lbs. Placing ninth was 2000 Olympian Kevin Bracken (Colorado Springs, Colo./New York AC) at 66 kg/145.5 lbs.