I have discovered that the Audi fan part number 443- 959-455-N can be used on
a Vanagon.
The Bosch motor housings are the same only 50 watts stronger.

It has a four blade fan attached, but is slightly larger than the Vanagon
three bladed fan.
I am considering modifying the four bladed fan to fit in the smaller Vanagon
fan cavity.
The hub is the same diameter. I will look at the pitch to see if there in
much difference.

I am also going to be putting in a 80 amp fusible link inline with the fan
motor so it can blow if the fan seizes and not damage the wiring.  Audi has been
putting one in line since 1991.  I have not looked at the Vanagons wiring yet
to determine if there is a fuse inline, if there is one, then no change and
if not one than change...

Also on the Audi web page, it says that blowing the low speed resister is a
sign that the fans bearings are starting to seize and pulling more of a load.