Yeah, I get the feeling that the people behind this knew a thing or two. This was 1950, just as the Kefauver hearings were in motion, so a lot of the material they covered wasn't exactly common knowledge yet.
I think the characters are each based on a few different people. The hitman who works out of a clothing store on Sunset calls back Micky Cohen's clothing store on Sunset. The hitman was Italian, of course.
I'm going to end up watching this one a few times. btw, I was thinking the girl who the main character likes, the one beaten by her jealous syndicate boyfriend, was based on Virginia Hill.