In Reply # 11 of this thread, . . . 2 pictures from the 1968 Assembly Manual, one of which showed the basic Part Numbers of both the Strap and Fastener. I was unable to find either in any of my MPC's.
Ford had a unique part numbering system, several in fact, that was rigid in the engineering phase, and "looser" on the assembly line. Briefly: Ford "design engineering" had a part number convention that used a 4 or 5 digit "base" number to identify a specific part and group of parts. With the addition of a "decade letter", a single digit "year number", a "product line origin letter" and a "responsible organization letter" as prefixes to the base, and a "letter" to signify variations which engineering may or may not have used, you wound up with a part number that looked like this
C7ZA-1234-A. The key was/is it avoided duplication. That wasn't enough, so a "model number" was incorporated into body part, part numbers - C7ZB-
6312345-A.
The "design engineer" was happy.
Then came the "manufacturing engineer". He had one underlying task -
keep the assembly line moving.
If the manufacturing engineer was building 67 Mustangs (and other Ford models), design engineering was finished with designing the 67 model year, probably finished desiging the 68 model year, and working on the 69 model year, and thinking about the 70 model year.
Speed was needed on the assembly line like RIGHT NOW. Some leeway was granted to the manufacturing engineer in "creating a special part number". For example, power steering parts used a four digit base number that started with the number "3". To avoid duplications (a mortal sin), a letter was inserted in the base number in the third position from the right - 3A555 (an example) for an assembly line required, manufacturing engineering authorized "we need it now" item. The general idea was to "make the formal paperwork later". The intent was to have design engineering incorporate that "specrial item" in future designs or make "something" for the service department to use. Quite often that did not happen. Once design engineering recognized what the problem was they redesigned the "situation", and the "quick fix parts" went away. That's why you won't find 6E523 or 3C696 documented. Ford Motor Company devised a "quick fix" system to do what the company needed - sell product.
Exceptions were and are common.
Jim