In Godfather 2 and 3 because of disagreements with Actors or due to unfortunate incidents new characters had to be made these were Frank Pentangeli and Joey Zasa, now my question is if Castellano and Spinelli hadn't died would the story's of their characters have been the same.

In Godfather 2 would Clemenza have been arguing with Michael over the Rosato brothers and have testified against the Corleone family?

Would Willie Cicci have really been so flashy, eager to enter the drug trade and actually betray Michael with the helicopter thing? This scenario seems plausible but Clemenza would be more level headed regarding the Rosato's in my opinion