The actor who was supposed to be The Godfather is Raf Vallone ,the one playing Cardinal Lamberto(later the Pope) in GF3.

As for the CNN story,Coppoloa said that Brando was VERY eager to play that role when he first came to see him about it in Brando's house.He said that Brando was sitting on the sofa,talking with the Don's "accent" until he go the right cords he later used in the movie.They both agree to go for it.Coppola insisted on Brando,but the studio didnt want him.You know who won at the end,and the rest is history