This C8ZZ-6510146-A Rocker Panel Moulding "Kit" currently listed on FB Marketplace caught my eye because of the C8 prefix, so I did some digging into the Parts & Accessories and Obsolete.Supersede.Interchange catalogs. My observations:
1. As of the 1960-68 catalog, change number 28, dated April 1968, the C8ZZ-6510146-A kit was not listed. In fact, there are no basic part number 10146 items listed.
2. Similarly, the 1965-72 catalog (dated 1975) does not list the C8ZZ-6510146-A kit either. However, there is a single listing under basic part number 10146, but for the Pinto (L).
3. There is no record of the kit nor the individual left & right moldings (C7ZZ-6510176-A / C7ZZ-6510177-A) with attaching parts in the 1979 version of the Obsolete.Supersede.Interchange catalog.
4. Both MPCs list the individual left & right moldings (with C7ZZ prefix) as viable service parts.
I have to wonder when this kit was developed, whether in 1968 based on the C8 prefix, or much later to serve the blossoming Mustang restoration community. I also have to wonder what catalog this would have appeared in.