Dustin,
When you ask what these starters come off of, the answer is a marine SBC. Don't try to put an automotive starter on it which I assume is why you're asking what it comes off of.
I don't have any specific part number for it but Ron and/or Dan may. They'll probably have one that they can get for you if you're looking to buy one.
Another option is take it out and to a reputable rebuild shop in your area for a rebuild.