rico_bob this is a 56 1 1/2 ton, from what I can see though the 52 years of grease and dirt with it in the truck it looks like it may be a standard BOP bolt pattern but I can't tell for sure I do know that the early Buick nail heads up to 63 anyway had a different bolt pattern that was round and nothing like the later BOP pattern.
Hot Rod Dad I am familiar with the Chevy and BOP housings I am not sure if this old of a motor 56 316 V8 Pontiac used the BOP pattern.
