I believe I read that Richard Conte was going to get part of Vito Corleone if Brando did not take it. I looked up Richard Conte, he had impressive acting career. I thought he was good. He had to be more low key in order to not have Vito suspect him. One of my favorite lines and scenes, where Brando says "It was Barzini all along" would not have worked if Conte played him as obvious villain behind the war.