If this was an option on the GT/CS, does it refer to the over the shoulder belt that was stored above the doors? Are they still available repo? My car lists them as an option, but are no where to be found. For that matter, someone removed the regular seat belts as well. Anyone have an extra set of black belts lying around they would part with for some $? Thanks! ???

the shoulder belt was standard on all 68 Mustangs (except convertibles). The deluxe seatbelt option was a chrome ring that goes around each belt buckle and a seatblet reminder light on the dash. Every 68 dash bezel has the provisions for the warning light, all it is a bulb wired to a relay that stays on for a couple of seconds when the ignition is turned on.

and here's the wiring harness

Thanks for the very detailed information! I will check again on the car, but I am assuming that the headliner was replaced at some point, and the shoulder belts were removed. Is the mounting kit available still for the belts?

If you're looking to re-mount the shoulder belts the mounting point is probably still there. I have a hard time believing someone would go through the trouble of removing it. They probably just covered it over with the new headliner and didn't cut the holes out for it.