Kid Hogan's weight is never given, but given his size, he is either a heavyweight or a light heavyweight. If so, the "Champ" he's supposed to fight would be either Joe Louis (heavyweight champion from 1937 to 1949) or Gus Lesnevich (light heavyweight champion from 1941 to 1948).
The Schermerhorn Gym, where much of the story takes place, is a stand-in for Gleason's Gym, which at the time of filming was located on West 30th Street and Eighth Avenue in Manhattan just south of Penn Station. However, in the 1940s, when the story takes place, Gleason's was located in the Hub section of the lower Bronx. In 1987, the gym moved to Brooklyn. Another possibility is the Kingsway Boxing Gym, which was formerly located on Eighth Avenue and West 40th Street across the street from the Port Authority Bus Terminal.