Hi JTJ
Mr. Schneider is correct in that Chevrolet called your vehicle a "panel truck".
They did however build it in 1/2 ton, 3/4 ton, 1 ton, and even 1-1/2 ton sizes.
1/2 ton was a DP, 3/4 ton a DR (as yours is), 1 ton was a DS, and 1-1/2 ton probably a PJ although I'm not sure on that one.
I found this:
http://home.znet.com/c1937/Prod.htmIt says that for 1946 there were:
2583 first 1946 model and 18614 second 1946 model 1/2 ton panel trucks
4002 3/4 ton panel trucks (yours was 1 of them)
2629 1 ton panel trucks
63 first 1946 model and 1098 second 1946 model 1-1/2 ton panel trucks
This source mentions Ken Kaufmann and David Hayward (both VCCA members I believe) as 2 of his sources, but I'm not sure where his figures for 1946 came from.
If anyone has other, or more accurate information, please correct me.
Hope this helps!
Ole