1974 Dodge Dart Bench Seat Problem

I have a problem on the passenger side bench seat. The seat back keeps popping off the hinge pin. The drivers side has a hole for a cotter pin and it keeps it in place. The passenger side does not have a cotter pin. I tried drilling a hole and broke 2 bits off in the process. It seems like it's OEM seats and hardware. How do you keep your passenger side bench seat in place? My wife didn't like getting spilled into the back seat when I gunned it at all.
:rofl: