Your truck serial number matches a '46 3600 (3/4-ton). The ADCA is the engine serial number prefix. That prefix is for the '216 used in the '46 3600 and 3800 trucks, so this truck was titled on the original engine, which may or may not be in the truck now.
Check this page for the location of the engine serial number. This number is stamped on the block, and as Fred suggested, the stamping could be filled with grease and crud and paint. The casting numbers could be concealed under grease, crud, and paint, too.
