Im pretty sure there is a bronze bushing style out there that replaces the roller bearing one. Goes in the torque converter register. You could hand drill the smaller pilot hole deeper to accommodate the end of the trans input shaft.
I think your friend means the rv has a 440 under the hood and a 6pk in the fridge.
But if your serious there are motor mount kits to put a RB in a /6 car and just use the trans thats in the rv.