1955 1rst. The '55 1rst and early 55 2nd Napco 1/2 ton systems are different from the later versions in that they actually used a 3/4 ton front differential with the 3rd member on the left side. It had a 3.90 gear, and the rear used 6 to 8 lug adapters to keep the wheels the same.
As far as WW2 Chevrolet 4x4s, the smallest I know of are all 1 1/2 ton. Dodge did make a 1/2 ton 4x4 in '41 for the military, as did IH, and I have heard of a few 1/2 ton Ford/Marmon-Herington conversions that saw military use. Might have to do a little searching to see if GM did the same.
