I definitely understand this. I'm not on a time constraint with this project. So no rush.

Which sections will have tight tolerances? I can't imagine the outside walls will have functionally tight tolerances. I figured the face that the barrel butts up against will have a tight tolerance and that's why I'm leaving as much of the original intact as possible. All of the faces on the inside of the magwell are original and in good shape. They just need some slag cleaned off. As far as the grooves for the magwell dust cover go, I can machine those after I get the other work done. I'm not worried about that. The barrel bore in the receiver is still intact as well.