Starter shims?

My set up: small block 408 69 A Body. The issue: squealing noise on higher RPM ( in gear and neutral ), about 1/4 inch of starter gear worn down. Doesn't make the noise at idle...
I pulled the trans, clutch, and flywheel to take a look, didn't find anything wrong. Put it all back together, still making noise. So I'm thinking shims...