66 Barracuda Shoulder Belts

I've owned at least a couple of dozen '66's (currently 9) and looked at hundreds more through the years and have never seen that dealer installed option. I saw that option listed in the owner's manual 30 year ago and was curious too. Never did find out for sure why it was in the manual and never an actual option. I suspect it was something on the drawing board that they hope to enact that year but at the last minute they decided to wait or changed their mind. I've inspected many bodies that I've stripped and couldn't find any anchor points that were reinforced good enough to use. You'd have to weld in a brace and nut to do it right. Then you'd have to figure out what kind of belt to use that will match the lap belts. The two separate belt units that they had in the '68 models were a real pain to mess with and storing them was just as bad. The shoulder harnesses always seemed to be in the way. Let me know if you find any documented info on that listed option.
Thanks, Mark