Keep in mind starting production didn't mean that there still weren't restrictions and rationing. The War Resources Board held control over all materials vital to the war effort. The Japanese did not formally surrender until September 2, 1945. Chromium would have been one of those restricted materials.
Most trucks in '45 and early '46 WERE hybrids. Trucks were the first vehicles allowed into production for civilian use. Most cars weren't permitted back into production forvarious reasons, including plant conversion, until between October of '45 and January of '46.
Having been involved in Studebakers, I can tell you there were many running changes between the extremely few '45 models and the end of 1946. Studebaker did have seperate model numbers for '45 models
You have to look at the times. There were no absolutes except what was put on a serial number or build plate. Most military vehicles had there own serial & model numbers. The production numbers on these trucks were limited to hundreds. The engine numbers for your truck should start with BG1001 or BL1001, depending on the engine plant.
Everyone wants a '42 or a '45 model. Easier to find a '42.
One thing about old cars. Just like anything else, if it walks like a duck and quacks like a duck...Missouri also used the date of sale for the year on the title. It was reasonably common.
If you don't want to here from others about the truck being a '46, I would suggest call GM. From this website... GM Resto Pak