distributor vacuum advance part nbr

[SteveO_71]

I would like to find the part number for the dual port distributor vacuum advance canister for my 71 Mach1, 351c 4V. I want to buy an NOS part as opposed to the generic repro part that is typically sold.

I know the base number is 12370 but dont know which letters are on the front i.e. D1FZ,C8AZ. I thought they were pretty much interchangeable between years and were the same as long as they had 2 ports.

However, in reading, it sounded like the more performance cars received a different calibration of vacuum advance. Is this true?

Hoping that someone knows the answer or can check an original part to verify the part number.

Thanks!