is this only a challenger problem? cause aprils cuda goes in fine.
the seat back goes in first. there are to hooks on the deck supports where the pressed cardboard is. the seat backs have to catch on the hooks before ya push the seatback down. then theres 2 bolts that mount the seat back at the bottom. (if these bolts are in bofore ya mont the seat, the seatback won't go into place) Then the seat bottom gets installed by putting it under the seat back and pushing it toward the rear of the car untill it catches the hooks on the floor.
hope this helps
joe