I recommend the convex mirror for the passenger side.
I replaced the stock flat one on my '81 with a convex
one from the BusDepot.  Much better and worth the price.

They just screw on from the outside.  There is a
gasket between the mirror and body--not plastic, not
rubber, but ????  Part 251 857 543.

The sliding door in the '80--'85 doesn't work as
easily as the later.  The latch design changed to
better pull in the rear of the door.  I have an '81
and an '87 and there is a BIG difference.  The '87
just slides and closes easily.  You can make the older
ones slide easy for a few days with some lube--white
grease sprayed or Triflo, but then it gets hard again.
Basically the door has to be moving fast enough for
the momentum to pull (snap) the rear in to latch.

Take care of the handles and latch; parts are getting
hard to come by.

                        Richard A Jones
                        Boulder, Colorado