OK something odd, I'd better be sure I'm talking apples and apples 
here, both the Bus and '81 Vanagon tanks are 6" diameter, the Vanagon 
tank approximately 30" long end to end if you measure to the tips of 
the round caps.  Now Manchester had told me the larger of the two 
styles they made was 8" x 30" (I had assumed larger meant Vanagon 
versus Bus) but perhaps there are two sizes for Vanagon years with 
late vans having the 8" tank.  What I'm getting at anyway is that 
extra 2" makes a hell of a volume difference, nearly doubles it in 
fact.  So for the replacement I'd want to bump to at least a 7" 
diameter or perhaps an 8" diameter if indeed that was stock later on, 
if not we'd need a discussion on the reduction of ground clearance 
the tank would cause.  It is of course far more effective volume wise 
to increase the diameter rather than the length of the tank, though 
I would in fact consider both, say a 7" x 36" tank.  With all this 
discussion of auto fill/stop valves as well, perhaps I need to know 
something about the later tanks in general.  The early have 3 ports, 
a VAPOR out, approximately 15.5" back from the front of tank, a FILL 
port 19" back, and the 80% tap (which on early Vans/Buses is merely a 
brass/rubber plug over a pipe that goes up to a high level in the 
tank) which you unscrew manually and wait for liquid propane to 
appear on filling.  Without going and looking I'd say these ports are 
3/4", 3/4", and 1/4" NPT respectively, the vapor and 80% must go high 
in the tank, the fill probably not.  Anyway anyone want to fill me in 
on the later tank?

John
vwbus@netbiz.net