Maybe I am missing something here. Is the starter grinding because the teeth on the flywheel are damaged or because the Starter bendix isn't fully engaging the flywheel. When I say isn't fully engaging I mean the bendix isn't extending completely and the starter bedix is not meshing with the flywheel. If this is happening the grinding is the to gears grinding face to face. If this is the case it maybe an electrical problem, not enough of it. You may want to check your ground cables.
This is just a thought since the starter was working fine before the gasket change. You may want to pull your cables and clean the ends. Or just replace the cables if they are old.
Good luck
