The repro 8400 starter I bought from Goat Hill had a much smoother surface than I would have expected for a starter it's age (no rust pitting), but he didn't take very much off the diameter if any as the screws still looked well countersunk. I have recently seen several "new" starters (bosch I think) that appear to be made from all new cases that in the pictures appear to be of correct configuration with no part number on them yet. Maybe that's where he gets his cases from?
Mark
Mark