I'm aware of no difference nor have seen any between the primer color nor the sound deadener application between the three plants that could be used to determined what plant the a car was built and the variations of original cars documented from each. So would not use that as a solid determining factor
Just saying 
Being aware that this is off topic, I will say that "lacking sound deadener of any amount" (on the bottoms of the flat area of the fenders) is usually a San Jose trait. It seems you have stated so in other threads. The somewhat salmon colored primer I found seemed consistent from side to side (with each cars date stamping of the metal being roughly 6-weeks apart).
Back to the upper hinge detail. The 2nd set of spare doors I have with the stamped upper hinge, is indeed a San Jose mid-December projected build date. Oddly enough, the other door that I have used since 1978 on my car, has close to the same dates on it and it had both upper and lower cast hinges. I can get dates easily enough off of the extra doors but I am not pulling the door panel to check the one in use (the replacement from 1978) and I don't remember taking picture evidence during the restoration. Mid to Later December stamp dates on the doors may be of assistance to the O.P. in determining whether or not to use both cast hinges or a mixture IMHO.
On edit, adding pictures and it looks like 17M date on the Data tag for the spare doors
12 5 D 3 found on the "1978 replacement fender" while on original LH fender was 10 18 3B is stamped, which is roughly 1/2 a month before my actual build date.
These findings combined with other Marti Reports and other Late December cars might help the O.P.
It's not easy with back and forth usages of both types of upper hinges.
FWIW. I found two variations of the Cast Lower hinges too! ...like two different suppliers. This was discussed in another thread too but it may add to Jeff's comment about my 1978 donor car NOT necessarily being a San Jose car...the plot thickens!
