I just got a 3rd row seat from a salvage yard along with the seat belt harnesses that hang from the roof. My truck never had a 3rd row seat, but the 2nd row had flip-up things for it and I noted that the roof had plates over where the seat belts would hang from. My assumption was that under the carpet was mounting points for the seat, but I was wrong.
The salvage yard had removed everything for me before I got there (!) and so I really didn't look at the truck it came from. I looked at mine and while there is absolutely nothing where the rear of the seat would hook in, there are caps around where the front of the seat would hook in, and under those caps are body-to-frame mounts.
I'm thinking now that to do this the right way, I'd have to replace some or all of the bed of the suburban and weld in one that was setup for a 3rd row seat. It's also possible that there's just a frame mounted on the floor that the seat hooks into. Does anyone have a 3rd row on an early 90's suburban and know how it hooks in? I'm not sure if it's another part I can get from the junk yard or if I'll have to custom fabricate a frame to mount it to. Had I removed the parts from the truck myself, I'd of noticed how it was hooked in, but no such luck.
Thanks,
--Jeff