I went from non to suspension and know the drill.
1) you need the bases AND the bottom frame of the suspension seat (noted, the flat based ones vs the non suspension that have a long leg on outside. $35 had an upholsterer in 24 hours switch the covers and rebuild the foam - such a deal!
2) Mot (thanks man) got me the suspension rib- I drilled out the spot welds on the wide non suspension one and used liquid nails to glue the new rib in- it is a $60 part from Toyota.
3) the rear seat tower has to be removed and I trimmed and folded down the carpet to be flush.
4) all the sheet metal bosses are there in the floor pan just the weld in nuts for the suspension bases are not so I used a nut, lock washer, and wide washer to bolt them in.
There is a little carpet slop from the front rib being smaller, but I only notice it when I vacuum the carpets.
ride is niiiiicccceeee.