Starter Shims

['76 Big Block]

Okay--- after a lot of procrastination on my part, I finally replaced a starter that was giving me problems when it got warm. It's close to the headers, and I'd put a shield around it, but the problem wouldn't go away (barely turned when warm).
What I'm asking about is the shims. I got 2 thin ones with the new starter, but there were a bunch (6) between the old starter and the block. They were marked with different thicknesses, so the total shim thickness was .120. I looked at the flex plate (ring gear), and it appeared from the wear marks that everything was okay--- pinion gear not too deep, etc.
Has anyone else used this much shim?
The sheet with the starter said gear depth was supposed to be between .020-.060
Just trying to figure out what's going on...