I know I am very late to this party but maybe this will help. Your truck would originally have had an octagonal head (B-10) key that fit the ignition and passenger side door. It would also have come with round(ish) head key (B-11) that for the glovebox. The handle style for your truck is the same for 1938 and 1939 passenger cars and 1939-1946 trucks. The passenger and truck handles are NOT interchangeable. The passenger handles have a back to back D shape on the end and the truck handle are square on the ends, The way that they lock is completely different. Trucks for 1939, 1940. 1941?? used a locking handle on the passenger side but in 1942?? the lock became separate and was located below the handle. Re-keying an ignition switch, door handle, or separate door lock is a no brainer for any experienced locksmith. Many genuine GM accessories such as gas caps and tire locks came with the regular GM B10/B11 key. Taking them apart to re-key them can sometimes be a challenge. They often do not share the same wafer and spring parts as the door and ignition. This is also the case with some glovebox locks. I have a 1935 Chevy Coupe and a 1936 Chevy 1-1/2 ton truck. I seldom lock the coupe. I drive the truck often but I never lock it. Like Otto, I usually leave the windows open and the key is often dropped in the floor next to the seat riser. My truck is not slick so it's very approachable and I'm not worried about kids on the running boards, in fact, I encourage it. I'm normally not too far away, but I don't worry if I stray farther. I figure it is unlikely that a would-be thief would know how to start and drive the truck.
