Like Jim, I did not find the C4ZA-3043 part listed anywhere. I checked 1964,65, 66 single year parts and accessories catalogs, and the 1960-68 master parts and accessories catalog.
The closest I found was from the 1966 catalog, with three unique parts, each with a different thickness. The only difference is the C5ZZ service part number as opposed to the C4ZA engineering part number. They are likely one and the same. Since this was a day two modification, Ford should have used the service part number - tsk tsk.