All GM starters came wih a factory brace bracket to support the front of the starter motor.
This bracket keeps the starter from twisting when cranking.
When you leave this required brace off, the starter motor twists on teh two starter bolts and cracks the
outer starter bolt hole boss on the block.
The fox once the outer bolt hole is cracked is to run a old style 55 chev starter motor that mounts to the trans bell housing instead of the engine block. There is a shee4t metal spacer plate that allows you to adapt this old style starter motor to a later V8. The spacer plate adapter plate goes between the engine and transmission bell housing. You still need a brace on the end of the starter motor to the block at the other end to take up the twisting force.
The small body mini starter should have this end brace too. Two bolts are not enough alone to suport the starter when its cranking/twisting on the bolts.
This adapter plate that allows using the old style starter motor can be bought over the internet.
have to search for the site.
The other alternative is to remove the engine and casti iron weld repair the cracked outer sterter bolt hole and redrill and tap. AND USE THE FRIGGIN $10 end brace on your starter motor.
Thats probily in your tool box somewhere.
If the OEM brace does not fit your mini stater fabricate as required using it as a start.
ALL trhe starters require 3 sopport points or the nose of the starter and or the starter bolt hole will be damaged.