After 7 years or replacing everything on the car except the body panels and paint, it’s finally driving! Still have a ton of work to do on it.

I just put a new starter and solenoid in my 66 Mustang. The starter grinds sometimes like it is not fully engaging with the flywheel. Do I need to shim the starter? It is a 289 2v engine. Has anyone else tackled this problem. Any advice is appreciated.