Mini starter PLZZUZUZUZUZUZUZZZZZZZZZZZZZZZZZZ

It's not a cheby...you don't shim a MOPAR!!!!.....unless your using adapters or aftermarket pieces.
Not to argue but....I once pulled a starter out of a stock Mopar with a 4 speed and It had shims. Anyway, it sounds like the problem is something else but I have a buddy that had to shim a mini to get it not to "spin"