All gear drive original starters bolt up to all engines for which they were designed, that is, B/RB, small block, or slant. They don't fit some industrial engines, heavy trucks, or older flatheads
But there WERE changes over the years in the starters internally, and there are at least TWO major sizes in power ratings (torque) which can be seen, generally by looking at the length of the motor housing.
Again, I'm referring here to the original "wound field" starters.
