Re: shimming a starter on a 5.7 89
Shims are available at many auto parts stores like NAPA. They are simply flat stock about an inch wide with a notch on one end that slips around one starter mounting bolt, and another hole that matches with the second bolt. Use a tin snips to notch that second hole so you don't need to actually remove the bolts to slip it in place. Just loosen the bolts a little, slip the far end in and then pivot the shim into place. Tighten the bolts. I also agree that shims are needed more often when installing a rebuilt starter than on a new installation. Some of the rebuilts have been rebuilt so many times that even the bead blasting of the casting removes enough metal to screw up alignment. In the auto world, even years back, rebuilt starters had a shim or two in the box.