The third row, by the seat of my pants. I copied from pictures, the angles and bend diameters from a non-correct year middle seat. I just widened it to be within so many inches of the upper corners and enough to clear the wheel wells. I'm happy with it and spent somewhere around $40 in materials. I could've done a little better with the sheet metal, but my mistakes are where most folks won't be looking. The lessons I learned made for a better job on the middle seat.
The middle seat, I copied a middle seat I had. I believe it was for a later year Suburban but I'm not sure which.
I also built both of them to use 3/4" plywood for backing, covered with 3" of foam, covered with the covering of my choice. I believe the foam and the Naugahyde was the most expensive of all the materials I bought.
By the seat of your pants rear seat frame looks like a stock factory seat frame. And a heck of a lot cheaper.
Good Job, Thank for the photos.
Sorry for late reply, I didn't add thread to my Followed Thread list so I never received a notification that you replied. You have to use the full editor to have your reply auto added to your Followed Thread to list. Quick Reply at bottom of thread doesn't auto add thread to your My Followed Thread list.