Same Transmissions? 1965 GMC and the Chevy truck of the same year?

[jonzcustomshop]

I think you will be ok, the 5 speed out of my 2 ton gmc 4000 bolted right up to a chev belhousing, and the spline for the clutch was the same as the one I pulled out of a chevy.

pretty sure that sm420 4 speed was the same chev/gmc

gm did use 2 different holes on their mt belhousing I am not sure what the break was, I would just measure the one you have and compare it to your gmc belhousing, if it is different those sbc truck belhousings should be pretty easy to find