Call Stan's Starter and Alternator Rebuilders in Pulaski, TN., 931-363-6373. Stan is a 2nd.-generation owner of that shop, and he's in his mid-50's or older. He's got a massive stock of cores and lots of new old stock parts that date back to the 1940's or earlier. I've been doing business with him for at least 30 years, with excellent results and fair prices. Another electrical rebuilder I use regularly is Todd's Auto Parts in Nashville. They go back to the T-model days, and if Stan doesn't have something for some reason, Todd's is my second choice.
Jerry