These are the later "Ford Service" replacements for the 64 1/2 to 66 Mustangs and probably the replacements for '67 to '68 6-bangers too. These are serviced by "C5ZZ" 1965 part numbers. I attached the pic of part the numbers on the Ford boxes for reference.
The "originals" had thinner mounting studs and used inserts for the emblem holes in the sheet metal to retain these. Those are "C4ZB" castings and are rare to find in NOS today. I have a pair of those for sale listed in the SAAC Forum