For anyone tracking data about this...My ELITE Marti report DOES call out for the deluxe seat belts option seperate from the interior decor group. Scheduled build date in San Jose of NOV 1, 1966, actual build date NOV 2, 1966. DSO 71, Los Angeles ordering district. You may wish to include the DSO for statistics too, it could also weigh into the results. For whatever else it is worth, my original set were Ivey Gold, Hamill & the belt's date codes tags were oldest being 39-66 thru something like 42-66 (could be 41-66, I cannot remember right now but not beyond 42-66 I am sure) Statistically speaking, January 1, 1966 was on a Saturday. Using Jan 1 as week#1, then week #39 (my oldest date code) would put it at October 1st. If the date code deciphering begins instead on the first Sunday, then the oldest date possible becomes September 25th for the oldest possible belt date code on my Deluxe seat belt set. TRANSLATION: My Deluxe seat belts were installed roughly one month after they were produced on my SJ example. This is simply "My example" and the date codes were NOT all from the same week most likely because of the vat they were in on the manufacturer's floor and eventually the assembly line. I feel confident in saying popular COLORS will change how fast a vat would be emptied/ordered. My guess is a BLACK color is the most popular color used, followed closely by Ivey Gold, then Dark Blue, I would say on the less popular colors (Red etc.) the dates could be further off.
NOW it gets really complicated...THERE WERE TWO known SUPPLIERS to Ford for Seatbelts in 67...Hamill & Robbins...GOOD LUCK ON THIS RESEARCH! Far too many variables here I think! It would be nice to know the root of when, where and why on the differences but until more original examples are KNOWN to be correct for any given example...about all I can assure you of is that my example was under a month from the assembly of the seatbelts as a sub-assembly to the actual build date of the vehicle they were installed onto.