There is an '86 Adventurewagen for sale at this site:
http://fierycd.net/AW/
Scroll down the big bunch of pictures until you get to the picture of
the rear seat.  I've never seen anything like it in a Vanagon before:
Three contoured seats, fold down armrests, three sets of seat belts.
And it appears to be original.  Anyone ever seen this setup before?