I put a 5.0 in my 62.  Dropped right in with a few minor mods.  In my case I had to come up with engine mounts because the 62 k-member is not set up for a windsor type SBF engine, BUT in 63 the 289 became an option so you can get 63 289 mounts and drop it right in.  You will need a front sump oil pan and corrisponding oil pick up tube This also means you will need to plug the dipstick hole in the block and change out the timing cover for one with a dip stick. What are your transmission plans??  if you go with an OEM 64 type SMF galaxie transmission it will not bolt up because the bellhousing in 64 was still 5 bolt.  You may be able to get a trans from a 65 and up gal, but I think the floor pans changed in 65 on the Galaxie so the trans crosmember and transmission configuration might have changed too.  If you put a modern transmission in as I did you will need to totally creat a trans crosmember from scratch.  I started out with an AOD in my Gal then swapped it out for a T5.  in both cases there was crosmember work to be done.  I am sure there is more but that is all I can think of for now.  Would love to here more about what all you have planned for the project.