just for temporary info:

there IS a retro-fit package for the rear seat belts in vanagons and i'll
post the tech bulletin tonight (if i can remember ... i was gonna do it
last night!).  my dealer (in atlanta) said it's about $75 per seat for the
parts. and i think i remember it going back as far as 1985, maybe farther
but i'm not sure ... that means that the little threaded holes are in the
metal, just hidden behind the headliner fabric and the little cardboard
panels.

note that if you have the air conditioning, you are gonna have to cut some
holes in the housings that come down the sides of the luggage area (1986-91)
for the straps to come through.

another note (again, from memory) is that ONLY the OUTSIDE seats are available
for retrofit. that is, the middle person on the rear bench gets no shoulder
belt, and only the leftmost middle seat person gets one. so out of five seats,
only three can be retrofitted with shoulder belts.

me, personally, i would NEVER buy seat belts from a junk yard: the car got
to the junk yard because of a wreck ... which might have damaged the seat
belt (if the seat belt did it's job and protected someone). of course, the
rear seats are not as likely to have had any occupants, but ...

i'll try harder to post the tech bulletin and the part numbers tonight.

joel