The typical Chevrolet repair manual for 1941 trucks should cover everything you need to know about 1941-47.1. I can't find mine right now, but I believe they cover everything from cars, to pickups, to the large trucks.
For more specific knowledge, you really need to know what your looking for. I have side manuals specifically related to rebuilding or repair of hydrovacs, 2 speed rear ends, hydramatic transmissions and so on.
Jeff
