Sticking starter
 

I have an 85 k5 military blazer, I just got it and noticed it didn't have a starter bracket, before I had time to get or make a bracket one bolt broke off. I got that replaced and made a bracket before I created any more damage. Now when I engage the starter, it either sticks on, or doesn't engage with the flywheel. Is this a shim issue??
I checked the solenoid, and bench tested the starter and everything seems to be working correctly. It has been converted to 12 v also.
Thanks for the help!