i have sucessfully added armrests to vanagon seats that did not originally
have them.  for example, i have added armrests to seats from a 83 westy.   just
drill holes in the seatback frame sides  and bolt the brackets on.    to acess
the back to put the nut on you will need to undo the upholstry at the
seatback bottom to slip your hand up there obviously.

you can also add vanagon armrests to any other seat that has a flat sided
seatback frame...

i have some armrests for sale if anyone's interested...

chris