In the novel, the chapter on the Don's war with "Maranzalla" loosely parallels the Castellemmarese War of 1930-31, with "Maranzalla" taking the part of Joe da Boss Masseria, and Vito Corleone as Salvatore Maranzano, the victor in that contest. The Don's life seems to me to be based on Frank Costello's, rather than Lucky Luciano's, as some believe. Also in that chapter, the Don arranges for the assassination of a hot headed Mafioso of whom he says, "but no one can reason with this fellow." That person parallels Albert Anastasia, who was actually mowed down by the Gallo Brothers on orders from Vito Genovese. Moe Green is, of course, Bugsy Siegel.
The movies, especially Part II, have many more ties to "real life." Hyman Roth is Meyer Lansky. The "Lakeville Road boys" are the "Mayfield Road boys" of Cleveland (Moe Dalitz et. al.). "Eddie Levine of Newport" is Eddie Levinson of Covington, KY. "Senator Geary" is Pat McCarren. "Frankie Pentangeli" could be Joe Magliocco, and the "Rosato Brothers" are probably the Gallo Brothers. "Johnny Ola" is Jimmy Blue Eyes Alo. And Part III has very strong, direct ties to Vatican III and the Vatican Bank scandal.