Re: AC in a Diesel Vanagon, I would talk to the people at ICE (ads in VW and
Porsche mags).  They are nice on the phone, and should know if it can be
done, why not if not, and how much their kit costs if there is one.

Re: where to put oil cooler, I've just put a front cooler in my 6cyl Vanagon,
behind the front grill after pulling out one panel of the front grill backing.
Have not been able to get engine oil over 185 or so since the cooler went
in, although 85 at 95 (mph at oF.) is the real test.  I used the same 
technology that aftermarket front coolers for Porsches do: 3/4inch hoses
running from thermostat to cooler.  In the Vanagon the hoses are about 15ft.
long.  Note that the Porsche six has a two stage oil pump, so the pump 
does not have to maintain engine oil pressure to the front of the car and
back.

In a 4cyl bus I would probably keep the cooler close to the back of the
car, but over the trans sounds pretty much out of the air stream, especially
for sitting in traffic.  Maybe under the floor in front of the rear wheel?
In any case I would certainly include a thermostat in any add-on cooler in-
stallation, so the engine doesn't have to push through the cooler when the
oil is cold.

B.
Wm Kennedy
kennedy@admin.njit.edu

PS keep my stock clutch in mind when you're volunteering my van for the 
bus races.