Just thought I'd show you my Subaru Brat rear seats . I wanted a modular set-up I could remove rather quickly if needed as I don't use them that often. I used 2"x2" angle for the side supports, then welded 1"x2" rectangular tubing to them for the cross braces. Picked up a pair of the seats on craigslist, welded their frames to my cross braces. Then welded tabs for seat belt mounts.Just using lap belts for now, the grandaughters aren't into anything tough yet. I'll get harnesses and extend my cage by then. With six 3/8" bolts and fender washers it can be removed or installed in a matter of minutes, and they love the handles to hold on to. Seats-$50, steel-$20 serves my purpose, and looks cool !IMHO
Alex
Alex