For a number of years (the good ones
) I drove a 1961 VW panel van. I just realized I don't have a picture of it in my album.
Anyways, the panels had a smaller back window than the Kombis; almost zero rearward vision.
I welded nuts onto the ends of the mirror arms (moved them out 1") and screwed on rectangular convex mirrors with acorn nuts for lock nuts.
No blind spots and no back bumper.