Sorry for the misinterpretation, but someone might find that 6A023 discussion useful someday
Let's switch to the 10692, which is the part number for the "member assembly - front floor cross no. 1"
According to the 60-68 MPC:
65-66 is C5ZZ-6510692-A (the 1965 single year MPC concurs)
67-68 is C5ZZ-6510692-B (the 1967 single year MPC concurs)
Per the 65-72 MPC:
65-70 is C5ZZ-6510692-C, so some typical consolidation has been done.
71-73 is D1ZZ-6510692-A
I would conclude that the initial design was changed for 1967, and then again at least once more in late 68 or 69 (a guess). The change to the revision C version however was such that it is backwards compatible.