Mine has the one piece back. And i just got split seats from an '89 IROC. I need the other striker bolt for the driverside. Does this bolt to the frame or is it just part of the interior panel?

it bolts to the body of the car, goes through the interior panel.

also theres a bar at the bottom to act as the hinging point in the middle, you'll have to come up with something for it. Or grind off one in the scrap yard and tack it into place in your car.

Exactly. Your basically looking at doing some welding. Your also going to need to get it in the EXACT spot or your seats are not going to come down correctly without binding. Good luck and have fun.