Mini Starter Help

Thats great that it all worked out. My son recently had the starter go in his 97 Dakota , being 19 and on a limited budget he took a non mini starter off the shelf in my garage , guess what it would not fit in the starter pilot , the older starter pilot is bigger in diameter . I doubt anyone would wonna go from small to big but i could see this happening if someone put a 518 auto trans in and tried using the same starter they had .