I wish I did have the info of what cars they came off of, but this is stuff that's been accumulating at my shop for forty years, most of it from cars stripped down before i started working here. From old VIN records and what i have learned from you and the other gurus here about distinguishing the different plants, most of the cars that got parted out were built in San Jose, which makes sense since we're in California.
Don't recall ever seeing those "clips" the date codes you posted don't seem to fit the "early" time period. And apparently you've not kept track from where this, now loose, parts came from (VIN or other identifiers). Were they found on cars produced from all three plants?
Sorry, to clarify "early" i mean the C7ZZ-6A023-C crossmember from '67 which was replaced by the C7ZZ-6A023-D for '68-'70. The most evident differences are the size and shape of the "notch" on the driver's side of the crossmember (see picture) and the width from front to rear at the center of the piece.
So to clarify - did you find them on automatic, 3 speed or 4 speed cross members. Will look through my pictures to see what I can find as far as any cars using these clips but need the application you've found them on since part numbers mean nothing to me looking at a car 
Yeah, i wish the stuff was marked better when it was taken off of cars. I'm doing my best to "back into" identifying parts using MPC's, OSI's, and Cross References, so I'm coming at the situation from the part number end, and using this and other forums for research I've been able to figure quite a bit out. It helps having several of something to compare side by side too. For example, there's two versions of the '69-'70 FMX crossmember, both under service number C9ZZ-6A023-A but having engineering numbers C9ZA-5059-A and C9ZA-5059-B. Even though the engineering number isn't stamped anywhere on the part, I knew there were two versions and looked through my pile of those to spot the difference(s), which in this case is the length of the holes where the trans mount attaches to the crossmember (7/8" and 1 1/8")(see pics).
The part number I see listed on a later MPC is the -B. Don't know anyone that has one of these that has had it out for a picture. Also don't know how many 70s were built with the larger engine but would guess those would be much easier to find for a resource
The C9ZZ-6A023-C shows specifically for the 1969 250E model, and was obsoleted early on (my January 1974 OSI shows it already gone and not replaced). The regular 250 in 1969 and in 1970-72 do show using the C9ZZ-B. I can't quite figure out the reason for this particular difference yet, but there were a lot of weird differences in drivetrain between the 1969 250 and 250E.
BTW for a guide IMHO part numbers are of little importance since the parts don't carry an engineering number and the part number doesn't relate to much after almost 50 years. Its more about the ability to identify them from one another or on a car. Just my experience
I would for sure include pictures in my findings. I use the numbers to give me a beginning idea of how many versions i'm looking for. Like the three iterations of the 1965 trans crossmember. Or the three versions of the 65-66 front vertical door glass channel (besides the service replacement without the plastic).
