All gear drive starters bolt up to all engines which were designed for them. That is, there are some heavy trucks, etc, which used different starters. That is, you can take a starter off a slant and install it on a 440-6 bbl. It might or might not crank as well as what was on the 440
But there ARE differences. Some are "heavier duty" and have a longer motor housing. Nowadays, most guys are going to "mini" starters. Mid 90's Dakota 360 for example.
