A kind listee provided a link to this "tank type" engine heater:
http://www.jcwhitney.com/ZEROSTART-TANK-TYPE-ENGINE-HEATERS/GP_2000837_N_111+10201+600001648_10101.jcw

I'm looking into it. The Mercedes adapter mentioned on the page has a
catalog number that their search tool can't find, dunno if that would be
needed to hook this heater - designed for 5/8'' hose -- to the Vanagon's
heater hoses or not?

Speaking of which, what hose would be good to cut to insert this gadget?
It looks like it wants to go into the heater hose loop somewhere, would it
matter whether it goes into the heater send or return hose? Possibly not.
Anyway, if someone has a good idea, the Bentley page and hose callout
would be cool.

I'm also looking for the rumored oil pan heater. It may be a chimera, but
there have been mentions of such things.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
Bend, OR
KG6RCR