How Are You Fastening Your Side View Mirror?

The mirror on my 64 kept loosening up. I bought the correct gasket from DMT and installed it. That seems to have fixed the loosening problem.

But if it persisted I would make a nut plate out of bar stock, say 1/8" x 3/4" long enough to be longer than the screw centerline dimension. Tap the nut plate in 2 places. Install it from inside the door and use 2 oval head machine screws with loc-tite through the mirror and door skin into the tapped holes . I'm guessing they woild be 10-24 UNC but you'll have to verify the size. 10-32 UNF optional.