I have done the rearward facing two person seat thing in my van.  I got an
old fold up table from a friend, and decided that the middle seat facing
rearward would be cool.  The grooves in the floor are not equal lengths
apart, so you cant just bolt the seat channels in a different location.  I
had to bolt the seat channels to a piece of 3/4 in plywood, and then in turn
I bolted the plywood to the floor.  I cut up the pieces of contoured foam
stuff to fit all of the odd parts of metal floor left uncovered.  We used
some carpet padding and van carpet from Menards to complete the job.

This arrangement has worked great.  We can still fold the bed down and
actually have seating for four.  We found some Sterlite brand storage
containers (stackable drawers actually) that fit in the spaces under the two
position seat.

Anyone out there that hasn't replaced the rear dome light with something
more substantial...  do it!!!  I got an RV light and wired it in where the
rear dome light went.  It lights up the whole rear interior (no more looking
for suff under the bed/seat by feel)