There has been a changing of the guard in U.S. freestyle wrestling, as five of the eight 2001 U.S. National champions claimed gold medals for the first time.    The tournament, held at the MGM Grand Garden Arena in Las Vegas, Nev., April 13-14, gave an early preview of the athletes who could be top contenders for the 2004 U.S. Olympic team.    Leading the parade of new champions was Cael Sanderson (Ames, Iowa/Sunkist Kids), the champion at 187.25 pounds and the Outstanding Wrestler of the tournament. Sanderson, a junior at Iowa State Univ., defeated 2000 Olympian Charles Burton (Bloomington, Ind./New  York AC), 4-1 in the gold-medal finals.    Sanderson has won three NCAA Div. I titles, and has never lost a college match. He was sixth at the 2000 U.S. Nationals, and was a 2000 University World Champion.    Two of the first-time champions have represented the USA at the World Championships, but never had been U.S. Nationals champions: Eric Akin (Lincoln, Neb./Dave Schultz WC) at 119 pounds and  Eric Guerrero (Stillwater, Okla./Sunkist Kids) at 127.75 pounds.    Akin, a 1999 World Team member, defeated surprise finalist Tim Dernlan (Huber Heights, Ohio/Ohio International), 7-1 in the gold-medal finals. Akin has been a two-time U.S. Olympic Team Trials runner-up.    Guerrero stopped 2000 U.S. Nationals champion Kerry Boumans (Colorado Springs, Colo./Dave Schultz WC), 3-2 in the finals. Guerrero was seventh in the 1999 World Championships, while Boumans was the 2000 Olympic Team Trials runner-up.    Other first-time champions included Bill Zadick (Coralville, Iowa/Hawkeye WC) at 138.75 pounds and Ramico Blackmon (Colorado Springs, Colo./Team Excel) at 152 pounds.    Zadick, a 2000 Olympic Team Trials runner-up, defeated Dustin DeNunzio (Cambridge, Mass./Dave Schultz WC), 3-0 in the finals. Blackmon, who was ranked No. 3 on Freestyle Team USA, stopped  2000 Olympic Team Trials runner-up Chris Bono (Gilbert, Iowa/Sunkist Kids), 6-3 for the gold medal.    The athletes who claimed U.S. Nationals titles for the second time in their careers included Joe Williams (Iowa City, Iowa/Sunkist Kids) at 167.5 pounds, Dominic Black (Ft. Carson, Colo./U.S. Army) at 213.75 pounds and Kerry McCoy (Bethlehem, Pa./New York AC) at 286 pounds.    Williams, a 1999 U.S. Nationals champion, defeated Byron Tucker (Norman, Okla./Sunkist Kids), 5-3 in the finals. Williams scored his winning two points in the closing seconds of the match. Williams was fourth in the 1999 World Championships.    Black, also a 1999 U.S. Nationals champion, defeated Chad Lamer (Coralville, Iowa/Hawkeye), 4-0 in the finals.     McCoy won the U.S. Nationals for the second straight year. He defeated 1998 U.S. Nationals champion Tolly Thompson (Lincoln, Neb. (Sunkist Kids), 5-2 in the finals. McCoy, who was fifth in the 2000 Olympic Games, was the only past Olympic Team member to win a U.S. Nationals title in freestyle this year.    The Most Falls award in freestyle went to Pat Popolizio of Cowboy, who scored four pins in 4:28. The Div. I team champion was the Sunkist Kids, with 85 points, followed by the Dave Schultz WC with 38 points. The Div. II champion was the New York AC with 47 points.