Sorry, I've been away from the site for a while.
I'm now wondering what kind of draws you have on this electrical system?
I would imagine that a stock 1949 generator-equipped vehicle was designed to support a very low (by modern standards) electrical load. Headlights, signal lights, perhaps a blower motor and windshiel wipers.
If you've added a lot of new loads ... say a killer sound system with a subwoofer or heated leather seats ... there's no way that poor old generator will be able to keep up.