regarding vanagon dual fuel conversion and where to put the tanks:

I've seen a dual fuel (propane/gasoline)  2wd westfalia with all the propane
tanks under the van.  There were at least 4 tanks manifolded together.  He
had two of the tanks where the spare tire goes, the spare was carried on the
roof.

I've heard of a couple air cooled dual fuel conversions in Calgary, but have
never seen one myself.  I'm sure I could
build one, only one thing different than water cooled.

I have my tank under the rear westfalia seat, a trade off for space but I
don't mind.

On another topic, I just completed converting my BMW 528E to dual fuel.

Gary
http://www.telusplanet.net/public/gary2a/rack/propane/propane.htm