First off, I must have been hallucinating... I am REALLY certain that I really did pull three sets of seatbelts out of the back, yet I can only find only four sets at the moment. However stuff is all over the garage.
My glove box shows 5 seat-belts. I have posted several photos. The first are from my car, appearing to be non-deluxe belts, but they were retractors up front.
I next posted what Classic Industries 'says' is correct.
My simple discrepancy is that if Classic is correct, I have a non-SS tire pressure sticker in the car with some really solid evidence that I have an SS. In addition to the trim tag, the rear-end matches as a 12-bolt as close as they can match. It had 3:31 non-posi gears (standard for Powerglide). The Powerglide tranny had a 21 tooth speedo gear and the valve body was date stamped Oct 66, exact same month as the intake manifold. Chrome valve covers, air cleaners and oil fill along with intake survived from the original car. Tracked car back to 1969, via last owner.
Hope the pics help. Will have to post several times.