It'll be a good tranny for a hot rod and with a shift kit/ good rebuild kit it'll handle around 400hp. The tranny in its natural form right now will not work with a 351. Before 1965 they had 5 bolt bellhousings, after that they switched to 6 bolt bellhousings. Just get one off a c4 that was mounted to any kind of ford small block or cleveland after 1966 and then it'll bolt up to a 351.
Oh, about the shift kit, a lot of manufacturers don't make shift kits for c4s before 1967. THis is because the 64-66 valve bodies are pretty primitive compared to the later ones. But, you can get a 67 or later valve body and bolt it in your c4. Just take note of what year it is from because there is some differences in years.