I've got a real, live RV propane furnace in my 84 vanagon.
Put it in myself and it works great.  It did take a little getting
used to, clicking off and on.  I worked one whole year in
Northern Michigan, including the winter, "camping" daily in
the bus.

These days, I am only out for short jaunts and never get
used to the clicking, so I take the warm bag and leave the
furnace off.

But I don't call sleeping in the bus "camping".  I grew up backpacking
so for me personally it never quite feels like camping unless
I get away from the roads.  Winter is my favorite time, also, provided
I can get away from the snowmobilers!

Steve E
84 vanagon
Lansing Michigan