I did the 3 to 4 speed swap in my 64. I scrapped a 78 for it's 350 and SM465. I used the removable hump from the 78 in mine. It almost fit, just some small mods with a hammer and a mig welder and I had a new floor,
Scott

Scott Ward

2 1948 1.5-ton Loadmasters
The red one and The snow pusher
1 1950 3100
1 1955.1 Chevy 6500
1 1954 Chevy 6500 2-Ton
1 1955 1st Series COE 5700
1 1963 K20 (454)
1 1964 C10 (350)
1 1951 1.5-ton Dump Truck
1953 and a 1956 Ford F800

Raising a teenager is like trying to nail Jello to a tree!