Quick Time bell/ started question

cant remember which applications use which but that starter was used on cars with a big stud and some cars with a trans or bell that had a smaller stud
you have a big stud version of the starter like all of them seem to be these days, and the bell has a hole for the smaller stud
hence the sleeve in the kit

i don't have a small block so i can't tell which hole was for a stud originally and which had a bolt

id find a standard small stud with the shank on it and see if the sleeve fits better
if the sleeve is loose in the stater i'd be looking to make a new sleeve out of ally or brass
or put a top-hat press fit sleeve in the starter hole and ream it to the right size for your chosen stud.

if your compression is sane and the flange on the bell is robust no support should be ok
loads of brand x cars have no support. on many the supported starter comes in the heavy duty option taxi police race/rally etc

Dave