I would also reccomend a careful inspection of the cooling tin.  All of
the tin, including the internal baffles actuated by the thermostat, should
be intact to give you the most efficient cooling and shortest warm up
period.  If an air cooled van has been driven without all of the cooling
tin I would be concerned that it has been overheated.  Also check the seal
between the cooling tin and the engine compartment as well as the seal
between the license plate and chassis.  These prevent warm air from under
the motor getting sucked into the engine compartment.

If you plan on using the heat at all I would also carefully inspect all
components that channel hot air from the engine compartment to the dash.
Pay particular attention to the heater boxes, riser tubes, and the things
at the end of the riser tubes that allow you to control the flow of hot
air to the dash.

I would also check the condition of the EGR system from the crossover tube
to central air plenum.  It is fairly common for the filter and associated
tubing to rust out.  When people see the price of replacements the most
common reaction is to tear out the filter and seal up the pipes.  Many
folks have run their vans like this with no problems.  I fall into the
camp of people who assume that the original engineers knew more about the
motor than I do, so I replaced mine with new stuff.  This is pricey, so
you might want to be prepared.

I can't think of anything else specific to air cooled vans.

good luck,
Jake
82 AC Westy