Rear upper. Since you removed the lower, look where the lower cushion was..you should see the 4 nuts holding the rear upper. Remove them and lift upward.
1. Push the seats forward, hop in the rear of the car and at the floor remove the one phillips screw holding the plastic shrouds over track to floor area.
2. Under those covers you will find one 13mm nut on each, remove them. (There is a second stud on the outter track, if reinstalling I put a nut on it increasing the number in the rear to 3)
3. Look toward the center hump by the console, there is a bar coming off the seat. Remove the phillips head screw holding it'* cover on and then using a T55 (I think?) remove the seat belt retaining bolt.
4. Move the seats backward until you have access to the floor to track covers on the front. Remove the one phillips head screw from each.
5. Remove the one 15mm nut per side.
6. Reach under the seat and disconnect all connectors and the airline from the floor to seat.
7. Lift seat and manuever out of the car. Front or back door is possible. If need be, reconnect the electrical to reposition the seat for easier removal.
00 Regal GS: All kinds of cool stuff.