Here is a solution which does indeed provide some heat to our 82 vanagon.
I went to Kmart and bought a $7.00 12-volt fan.  I then removed the grill
on the cabinet beside our fridge and placed the fan inside the cabinet.
Oh, I also dismantled the fan, cut its wires and wired it backwards.
We place a towel over the top grill (behind the gas stove), and start
both the fridge and the fan running.  The theory is this:  the fan will
pull heat off of the fridge exhaust vent and blow it back where we sleep.
This technique does seem to work to give at most an increase of about 10
degrees.  We also put a sleeping bag over the foot of the bed to keep
as much of the heat in as we can.
Since the motor puts noise back into the circuit, you might want to
take two inductors and two capacitors and wire as shown:

+ ------- inductor ---------\
     |                |       \ 
     cap              cap      fan
     |                |       /
- ------- inductor ----------
In order to hold the fan, I cut a rectangular piece of plexiglass and
drilled two holes in in:  one to hold the fan to the plexiglass and the
other to hold the plexiglass to the cabinet.

This technique is still in development, but it is sure a lot safer than
using the stove, which will kill you.  The biggest problem that we have
with this is that our fridge goes out at night sometimes and then the
exhaust pipe gets cold which means that I get cold also.  If someone could
solve that problem, we are well onto our way of heating these vanagons
in a very simple manner.
Stuart Hutton