It is so interesting the way that Puzo and FFC have synthesized characters from the pool of real life underworld gangsters. I've always maintained that Vito is modeled mostly on Joe Bonnano, Clemenza on Joe Profaci, and Pentangeli on Joe Magliocco. I also think that the Rosato brothers are the Gallo brothers.

You're probably right about Zasa, but I think his recruitment of blacks and puerto ricans models Joey Gallo more than Columbo. Again, both authors may have had a primary model for any one of their characters, but their overall characteristics seem to be drawn from a variety of real life personages.