A bit of belt-trivia.
Only Mustangs (and all Fords) built after Jan 1 had to have shoulder harnesses. It was Federal law. To pay for the shoulder harnesses, Ford deleted the louvered hood as a standard item for '68 (except, of course for the GT/CS).
I once rode in a friend's '66 Fastback, done up like a Shelby "R" model, and it had five-point belts--and a full roll cage. We "flew" across San Diego on Highway 8 in third gear at about 80-90 mph (here and there). He had dual quads on a modified 302 with a racing cam, and 4.11's. Pretty cool--and I felt very safe.
ALL OF YOU should check your original belts, to see if they are old and rotten. Old belts can break at the prime moment! Snake Oil Products makes repro belts. Check it out. Also check all of your bolts, and anchors for rust, etc., from the underside.
Good for all of you for wearing your belts! I remember as a Kid, we had a new '62 Falcon wagon that we took camping at Lake Tahoe. We got seat belts (and backup lights and a roof rack) all as options. The belts looped through this huge silver buckle, and then you sinched it down. Those Falcon seats also had those dang plastic seat covers with the little bubbles in them, that left goofy marks on the back of your legs when you wore shorts!
Paul N.