Let's ask the obvious question. What do you have now?
I just saw your spreadsheet Jim, you have two listed; C5AF-B and the C5GF-C. What is the difference besides the diaph column?
Looking at my source materials, the curves might be different, and the internals of the diaphragm to obtain those curves different as well. A DD-9 is an older type of diaphragm, DD-190 being newer (both are difficult to locate and are expensive).
Might be time period related - will let Jim handle the details
There is some confusion created by Ford as to 64 1/2 and 65 Mustangs all being called 65 models. C5GF-12127-C was show as being a replacement for C4GF-12127-B but for 65. That may be due to the 64 1/2 anomaly.
An October 64 build is a at least a month, maybe two, into regular production, and by that time the odd and leftovers may have been resolved.
Jim