In the history of Chevy truck bell housings, 1954 was a dividing year. 6 cyl. truck bell housings before 1954, had a flat or square bottom where the mount is located. 6 cyl truck bell housings starting in 54 and continuing through ? "not sure of the year" are angled where the mount is located. This also applies to the V8 truck bell housings. Because of this a V8 bell housing will fit a 54 chevy rear cross member.

The V8 passenger car bell housing has a different mount. They are attached with 2 bolts at the front of the housing, whereas the truck mount is attached with one bolt through the bottom.