Dave - the reason the Buick moved those old Flxibles was more the rear end gearing, as with the big bolts ... and they were doing it thru our venerable ol Chevy crash box 4 speeds until the 50's

the Buick FB320 has about the same HP and torque as a 70's 350 V8 .... I had a '47 Buick that had factory dual carbs and a 3 speed. was a great highway cruiser - the old Buick 3 speeds are scarce now because flat trackers liked them
Pete -
this page may be useful if you get the engine, and watch e-bay for parts, even complete 'take outs' from the old
Flxible busesBill