Well, I believe that things happen for a reason. The irony of his story being published when he wanted to go change it was proof that he was right the first time as we as people often go back and second guess ourselves. Personally, from knowing the movie as well as i do and reading the book, I would say that the Godfather movie is a direct reflection of what the rewrite would consist of. He and Coppola wrote the screenplays for the Godfather films. Granted had it actually been in novel form, some of the stuff that's not included in the movie would have probably been changed, but for the most part I'd say Puzo did his "re-write" in the movie's screenplay.