As I've pointed out in posts elsewhere, Clemenza, like Vito, is something of a composite. In this case, a composite of at least Joe Profaci and Joe Magliocco, maybe others. Profaci was extremely loyal to Bonanno (even though he was a Don) just like Clemenza was loyal to Vito. Clemenza took over the olive oil business and Profaci was king of olive oil. Although Profaci died of cancer,it wasn't before he got into a shooting war with some of his own men just like it's implied that Clemenza had disputes with the Rosato brothers before he died. Profaci's succesor Joe Magliocco (Pentangeli) died of a heart attack. In fact, the attempted strangling scene in the bar of GFII may have been a reversal of the attempt on the life of one of the Gallo brothers by a Profaci crew.