Jonathan described the first trip in "The Whale," a '76 Bus, with a 2000cc
FI engine.  Sounds like it was a good road trip, even with the starter
problem.  Averaged 72 MPH?  Whoa!  What was your top speed, and how long
were you able to sustain that speed? 

I drove my 1970 Camper from eastern New York to eastern Ohio (about 1000
miles round trip) on the Easter weekend.  The van has a 1600cc stock engine.
I averaged 50 MPH, and got 25 MPG.  It is slower than the later Buses, but
less expensive to run.  If I really needed to, I could pull the engine at a
road side rest area without worry.  Very easy to work on, and the parts are
inexpensive.  So if you are not in a hurry, and money is in short supply,
I'd say IMHO that the 1968-1971 Buses are your best bet. 

Wolf