I believe all the bell housings car or truck up to 1967 had the same size hole for the bearing retainer. I'm going by having swapped 3spd to SM420, and passenger car 4spd. In 1968 GM went to the SM465 and 435 in their trucks which have the larger bearing retainer. The 68-72 truck bell housing should be able to replace those in earlier trucks with the exception of the hyd clutch and 235 engine. If I'm wrong I'm sure I'll hear about it.8-)

Larry

I don't own a vehicle that isn't old enough to drink.