I always believed that the Lupertazzis were loosely based on the Gambinos. Carmine=Carlo Gambino, Johnny Sack=John Gotti, Little Carmine=Thomas Gambino. Plus the leadership instability and that they were based in Brooklyn (the Genovese have a strong Brooklyn presence, but are based in Manhattan and the Bronx).
In the end, however, if they are based on any family, it was a VERY loose connection. Chase never did let the real Mafia get in the way of the show.