The Godfather was shot using "grainy" film. It was done on purpose for style reasons. Though it should look and sound great, don't expect the film to look "crisp". It is SUPPOSED to look rough around the edges.
Trivia- the cat that jumped on his lap wasn't in the script. It was just a cat on the set. Worked so well, and added so much to the production, they went with it and built on it. A true actor, staying in character and working it when a cat jumps up. He must've instantly realized the dichotomy of that character's coldness, and the gentleness with a cat.
Yeah, and since I already spent $60 on the DVD set when it first came out, this is one that while I would really love to have it in a HDM, think I'll wait for the price to drop.
I suspect that while it will be nice to see it in HD, the reality of the 30 year old film is that nothing they do to it will make it look like the stuff actually shot today. Still... very very tempting