Looks from the pics like it used to be a 3-on-the-tree car but now is a T350.

In any case FYI, Ive run the Gonkulator on a couple such swaps, usually the swap from Powerglide to T350 makes it about a full second and 1-2mph better in the quarter especially with tall 3.08 gears.

Not sure if the 64 still has the dropout rear or that ended in 1963?