This Reply is intended to address the "Seat Belt issue" only ; specifically Standard versus Deluxe for the Console Option.
I will first note the sources used, and then my conclusions.
1) 1967 Showroom Options Book (typically these were available at Model Introduction)
No mention of Deluxe Belts required with Console.
2) Mustang Sales Brochure (Dated 8/66)
No mention of Deluxe Seat Belts, but does note that "Radio or AM-8 Track required.
3) 1967 Ford Car Facts Binder (Mustang pages Dated 10/28/66)
No mention of Deluxe Seat Belts, but does note "Radio required".
4) 1967 Salesmen's Manufacturers List Price Book (Book Dated 11/07/1966, Mustang pages 10/17/66)
No mention of Deluxe Seat Belts, only that "Radio required".5) 1967 Interior Assembly Manual (page on "Console Assembly" Dated 12/16/66)
No note in regard to Deluxe Seat Belts being required (possibly a later version may have said note)
6) Mustang Sales Brochure (Dated 1/67)
No mention of Deluxe Seat Belts, but does note Console (Radio or AM-8 Track required)
7) 1967 Salesmen's Manufacturers List Price Book (Book Dated 05/29/1967, Mustang pages 03/10/1967)
Notes Console(Radio and Deluxe Seat Belts required)
1967 Interior Assembly Manual (page T7-8695 on "Seat Section" Dated 03/28/67)
Notes Deluxe Seat Belts are "Mandatory with Consoles".
9) TSB Index for January 1966 through December 1968
Shows nothing related to Consoles and Seat Belt requirements.
10) 1967 Special Service Letters (by no means all that ere issued ; only the several I have)
None related to Consoles and Deluxe Seat BeltsBased on the above, it appears that sometime between January 1967, and March 10, 1967, the requirement was added the Deluxe Seat Belt Option be included with the Console Option.
Of course the best way to confirm, as well as narrow down the time period, is with known original examples, or their Marti Reports.
As a start, drummingrocks, what was your build date?
Hope this is of some help.
Bob