The 352 of that era was not a small block. It was one of Ford's "FE" series big blocks.Good question. According to the original paperwork it came with a 352 but I'm open to suggestions. I want to stay with a small block so I don't run short of room.
Which means the mounts, bell housing and accessory brackets you have should fit the entire spectrum of FE blocks including the 390 and even the 406 or 427 of similar vintage.
My mom's '64 Galaxie 500 had the 390 and it was a really well balanced package that cruised nicely and got about 16-18mpg on the hwy.
Ford made millions of 390s for everything from performance cars to 1 ton pickups.
They should be the most available, but you may end having to get a reman rather than a new crate engine if you choose to stay with an FE series engine of any size.
Sounds like a fun project.
Good luck with it and keep us posted.