FE starter

I think there is only one starter motor that fits all FE engines, manual or auto trans. Old part number on rebuilds was 3131. Three bolt nosecone. That is what mine uses, on a FE flywheel and bell housing. (1958 block)
I have heard that on some of the early 60's auto trans that the starter motor case needs to be ground down in one spot or flattened in order to have it sit in the bellhousing straight. I don't really remember exactly what. But the three bolt nosecone will bolt up. If anyone else knows............