After a bit of research it seems the AUTOLITE stamped C5AZ-12370-A would be the correct vacuum advance unit for the FoMoCo C5GF-A distributor ? Is that correct ?
Brian,
In a word - yes. It is also identified as "Motorcraft DD-190", the service stock number for C5AZ-12370-A. It is RARE.
No FoMoCo vacuum advance produced ?
Yes. It was documented as an "engineering part number" which was used to buy, inspect and stock until it was used to make almost all the 64 thru 67 V8 distributors with a vacuum advance on the assembly line. The DD-190 and C5AZ-12370-A are service
stock numbers for dealers' service departments to use as replacement parts. When they need to get new ones to put on the shelf (aka inventory) they used those numbers. Somewhere down the ordering chain, there would be a cross reference to use the engineering part number to manufacture new ones. That's the Ford system, which is similar to GM, Chrysler, the Federal Stock Number System, and even Home Depot to order new parts.
Jim