Until sometime in the 30's GM make 1/2-ton and 1-1/2 ton panels. I believe the 1-1/2 ton had duals. I think that cut-off is 1937 or 1938 but I don't recall exactly, and it was a little before my time.
By the time the Advance Design trucks came out GM was making 1/2-ton and 1-ton panels and they were all single wheel designs and far as I know any GM Suburban, panel, or van you see that was made after 1940 that has duals is someone's custom work.
