Well I stepped in and went right over my head on this topic.
Did a little reading on 1937-8-9 Delco generators.
1 post, 2 post and 3 post generators. Come back?
Early generators used a cut-out (poster's second picture).
Add to this GM rebuilt generators had another part number.
My head is starting to hurt.
1939 was a design transition year. 1941 all production goes for WW2.
Someone with historical knowledge and experience is needed.
I'm satisfied with the 6 volt system in my 55 1st truck.
I can still get the correct parts I need.
If you are not going 100% original and want to stay with 6 volts, I would definitely update the generator and regulator to the newer 50's design.
