Ok- I have tried shimming both sides even and each side one at a time. Nothing is stopping my starter from dragging. The flywheel looks fine! I even put a new starter on and same thing!

It will engage, turn the car over, but then it drags and makes that sound!
Someone told me it could be a voltage drop problem? If so, where should I start looking? I have a voltage meter and it shows 12.5 at the + starter post.

The guy a bought the car from has a ground strap from the frame to the outside starter bolt head. Just FYI. Is this normal?