I do wonder though this - since the service part is a C3 part, and pertinent to several years and more than one car line, why in the heck would Ford make a C7, let alone a C7Z specific part? When you consider radiators for example, due to the cost and size, it makes sense to spend some money for 20 versions across a million cars, saving 50 cents here and there. When going to a much lower service volume, the versions are reduced dramatically. Its all about cost/profit. A little old glove box light fixture done this way boggles my mind. That is really why I posted the question. I knew/know the difference between factory and service parts. Does this line of questioning make sense?
This is
pure speculation:
1) Engineering created a C7ZA part without realizing the C3AB part would work, or simply didn't realize a compatible part already existed (missed it in a search).
2) When the part number was created, the plan was to create a unique part, and instead they ended up with essentially a copy of the C3AB part.
3) The C7ZA part was intentionally the same as the C3AB, but that part number was "too old" so they pulled a C7ZA assembly number. I've seen a few cases where it appears to me that Ford created a new number for a part that appeared to be identical to a part used perhaps 5-10 years earlier.
I'l reiterate, these possibilities are reasons I can think of why Ford
might have made a '67-specific part number. I have no evidence that any of these scenarios took place. But these are the kinds of situations I see in my day-to-day experience in manufacturing. And while cost and profit are the primary drivers, sometimes choices are made for other reasons, such as reducing assembly errors, or because of problems with a supplier. And sometimes people make decisions that unintentionally end up costing
more money; it just happens. Especially on minor detail items like this - they tend to get a lot less attention and scrutiny than big, expensive, complicated components.
When you consider how much work goes into each and every component and fastener in a vehicle, and how many vehicles and TYPES of vehicles Ford made (and still makes), it is astonishing how well the system actually worked. Sorry, this stuff fascinates me and I get a little carried away sometimes!