Heading into its 50th anniversary on Sunday, the Nevada City Classic's all-time champions list leaves little doubt the caliber of cyclists who race here each Father's Day. It reads like a "Who's Who?" of American cycling.Of course, Lance Armstrong (2009) and Levi Leipheimer (1998) have both won here.The first man to win Olympic cycling gold for the USA, Alexi Grewal (1993), once stepped to the top podium spot on Broad Street. And John Howard (1970), the former Olympian, four-time U.S. Road champ and winner of the 1981 Ironman Triathlon in Hawaii, is also on the list.As often is the case …