Yesterday I swapped in a third row seating into my 2002 XL7 4wd.  I didnt take any pictures but thought I would at least document for others what needed to be done.  The donor was a 2001 XL7 2wd.

First of all, you will need the donor vehicle.  You cant make this work with the seats alone.  The most of the mounting holes are already in place.

On the donor vehicle, remove the storage box, seat, seatbelts, and lower side interior panels. Your interior panels wont have cup holders so keep them.
There are six brackets that are spot welded to the floor that support the rear seat cushion and the storage box that goes behind the seat.  Measure their locations and drill the spot welds out.  Clean them up so they can be rewelded.

On the vehicle receiving the seat, remove the rear carpet ad styrafoam underneath.  You will find that four of the holes you need to mount the seat are filled with things that look like large rivots.  They are actually bolts that have had the heads broken off to make them sit flush.  Weld a bolt to each one and turn them out.  I tried a chisel to spin them out but they didnt budge until I had welded on them.  I suspect they may have factory loctite.
Drill the spot welds out on the two brackets that were supporting the styrafoam floor.  Using a spot weld drill bit will allow you to remove the bracket without popping holes through the floor.
Clean the areas needed and weld in the six brackets removed from the donor. Take your time and weld small spots at a time.  The gas tank is underneath and you dont want to pop holes in the floor
Install the seat belts, side panels, seat, storage box.  All the really important bolt holes that would matter in a crash are already there (I.E Seatbelt and seat back).

Total work time- about four hours.

Now call all your buddies and volunteer as designated driver.