Chris smilingly asks
"hmmmman diesel vanagon w/ a/c........how Slooooooow can you go??? :<)"

I ran the numbers on that a couple years ago.  If you assume:
1.5 liter 48 hp. diesel Westy top speed = 62 mph
1.6 liter 52 hp. diesel Westy top speed = 65 mph
Which appears to be typical, then adding the AC load, I project their top
speeds to be
1.5 liter 48 hp. diesel Westy with AC top speed = 58 mph
1.6 liter 52 hp. diesel Westy with AC top speed = 61 mph

When it's 101 degrees F. and you're leaving Orlando for Palm Beach, which
suffering would you elect to endure?  Suffer the heat, or kick on the air and
suffer a 4 mph speed loss?.

But as I recall the official VW rationale for not installing AC in diesel
Vanagons and Westys was the stock cooling system's marginal heat rejection
capability.  At full throttle it won't affect that diesel whether the last
marginal horsepower goes toward developing faster vehicle speed or toward
compressing AC refrigerant.  But that diesel surely might be affected by
putting an AC condenser in front of its radiator.  That would both preheat and
restrict air flow to the radiator.  I'm not saying it can't be done, but I
think it may need some other system alterations to dump the engine's heat.

Has anyone  cut into the rear side panels to place a long thin radiator in the
air flow that could pass through those high side louvers behind the
Westy/Vanagon rear windows?  Does anyone know of a heater core radiator sized
so it would fit in there with the air flow passages oriented correctly?

I've read about repowered Vanagons with additional radiator capacity mounted
beneath the floor.  But exposing a radiator to thrown road stones and other
road hazards is a though that hits my reject button.
Comments?
John