Shoulder Harness PA32 Rear Seats

[Sp07R]

Has anyone gone though the process of adding rear shoulder harness to a Cherokee Six (PA-32-300)? Mine is 1967 with four rear forward facing seats. It seems like Alpha Aviation, BAS and AM Safe have the belts, but Piper apparently no longer produces the harness kit from their service bulletin 896. So my question is, does the Six have rear harness attachment points factory installed? If so, it seems any STC or FAA replacement will be fine, but I'm really unsure how to go about hunting down the attachment points or alternatively the kit from the service bulletin if not.

I'm hoping to avoid paying for somebody to pop open the headliner until I know what to expect... I'd have no idea what to look for if I tried this myself.

Any ideas or insight?

Thanks!