You have a great website! I am particularly interested because your father and I probably have something in common - a stay at lovely Fort Sill. I know that Sill is currently the only basic training site and HQ for Army (and Marine Corps) artillery; I'm not sure about the WWII era.
After my officer basic training in Quantico, I spent 20 weeks there training to be an artillery officer in 2000. I didn't change my MOS until - as a condition for further employ with the USMC - I was told to go be Commo. (For the first 3 years of being a USMC officer, you are pretty much on a probationary period. That allows them to cut the dead wood before they get to be captains and do things such as forced MOS changes. I was not happy.) I did thoroughly enjoy my time as an arty officer (don't call a Marine a "red-leg.") We worked on the M198 155mm - the only artillery currently in the USMC inventory.
Woo-hoo! I'm a sergeant now!