Wil  wrote....
My 80 Vanagon also had AC in it originally...a previous owner removed the
compressor...

The hoses, etc. are still in tact.  Can anyone give me any idea what kind of
performance impact/horsepower drop I might expect if I reinstalled it?

Can I use today's refrigerants or am I stuck?
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 Dear Wil,
        I have owned three 1980 Vanagons with AC. Some had an interior roof
mounted unit with freon lines coming up behind the drivers seat and drain tube
going down behind the passenger seat (nice unit). And one was an under the
front dash unit (it wasn't to good).
 I do know the clutch drive for the compressor was very hard for me to find
one time.Hope yours is O.K. If you need one I have an extra.
 If you have the condensor mounted underneath and are going to change to 134
type coolant you might want to add extra fans or add an extra condensor (maybe
up front like the water hauler vanagons) . 134 coolant works great going down
the road (where air can flow over the condensor) but in traffic(where there is
little air flow) it lacks the quick ability of freon to condense. Thus it
cools less. By adding a fan or extra condensor you condense the 134 more thus
more cold air inside the van when it evaporates.
Hope this helps.

Bill Webster
Meridian,Ms.