FYI, i have the middle seats and floor tracks/rails for sale.

install is relatively simple.
 every vanagon made is equipped with threaded welded in nuts in the floor for
the middle seat rails, weather its a camper, a panel van, whatever.   only
the pickups dont have them.
anyway, these holes are filled with plastic dummy bolts, to keep water out.

drill up thru these plastic bolts from underneath your westy..and up thru the
plywood subfloor.   these will tell you where to mount the rails.  place your
rails over the holes on top of your plywood subfloor..mark the outlines of
them..  and then use a circular saw set at the depth of the plywood to cut the
slots out of your floor..  then the rails drop into the recessed slots....bolt
them down.    use small strips of wood to fill the recessed tracks when middle
seat is not in use..and cover them with the carpet mat.

there you have it.. not hard.

chris