A few comments based on my 10+ year learning and work journey restoring Sparky, a ‘46 Chevy 1/2 ton.
If the subject truck is a ‘46, there are clues that it is, but it appears to have had at least one modification. The bed boards would have been painted black and bed wood was yellow pine, instead of what appears to be oak.
The gas filler grommet being leather would likely be correct for an early post WW2 model. Rubber was still in short supply because of the war effort.
That the truck has an engine apparently cast in 1940 and a maybe a few parts from other earlier model year(s) parts would not necessarily be a problem. The first months after consumer vehicle manufacturing restarted, demand was high and parts were in short supply, so manufacturers used what was available. Using a car engine in the truck would seem to be unusual, but not necessarily an impossibility under the circumstances. As suggested by Jim, checking numbers on other parts would be helpful.
Sparky was born in June 1946 and has “DP” as a prefix to its serial number. It came with the leather gas tank grommet. There are seven bed boards and fenders are bolted as shown in the OP photos and as Jim reported. Its other parts casting numbers match ‘46 production parts.
