Older vanagons, at least the diesels, have a painted steel dash with no
padding. This makes them useful for using heavy-duty magnets to hold
things down. I've always wanted a magnet for a 12v fan, and I recently
got one. Harbor freight has welding grounds on sale for half price,
under four dollars.

Throw away the spring and ground screw from the center. Glue some
headliner material to the bottom (2 reasons: it won't scratch the
paint, and without some distance between the magnet and dash, you
almost can't pull it off with your hands) Most fans I've seen have a
provision to screw the clip-on base into a shoe for permanent mounting.
Screw the shoe to the magnet and attach the fan to the shoe.

Now you can have a fan anywhere in the van you can find a metal surface.

If you want a photo, just ask.

Next I want to use two of these magnets to mount a rain awning over the
sink-fridge window. Will post that when it happens.

Jim