Another option is to make mounts to convert a so-called window-mount
mirror to fit the VW doormounts. This way no holes need be drilled in
the doors, and wiring can pass through the door's original openings,
also present in early vehicles.

This is what I have done, though the mounts I had cast are STILL with
the engineering outfit to do the CNC-milling.

I carved pieces of balsawood to the right shape, sanded them and had
them cast locally. The result was solid rough-surfaced blanks needing
machining; note that the blanks are slightly smaller than the wood
originals.

Once I get them back I'll have to finish the surfaces and powdercoat
them. Once that's done I'll be able to fit them & take images for
those who want to see them.

The mirrors are chrome-backed Hilux Surf SSR (=4Runner) LN106 &
LN130, larger than US & Canadian-market 4Runner mirrors. They will be
available in Canada, where LN100-series are now coming in used from
Japan. The switch I have is a BJ70 Cruiser, so I'll want to snag
something a bit more modern, say a 90s Corona unit.