That's right Alvin - the high cab was produced until mid-1936 and at mid year the low cab came into being. So the 1936 low cab was the 1936 Second Series with the high cab being the 1936 First Series.
In 1937, the low cab was made for the full model year, but the 1937 cab was slightly different fom the 1936 cab. The 1936 still had some wood in the construction of the door pillers and under the dash. It also had a slightly different curve to the windshield and, although the 1936 cab windshield looks like the 1937 cab windshield, they are not interchangeable. The interior door panels were also different from the 1937 in that they had leather strap door checks whereas the 1937 had door checks built into the door and the door jamb. The 1936 and 1937 cab had an under the seat gas tank with the filler under the passenger seat. In 1938, the filler was on the outside right side of the cab even though the tank was still under the seat.
Excellent response--but my 36 does have the gas tank in the rear so that might be the standard for the low cab series.
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1936 was the last year for tanks in the rear of the truck up into the 47-55 series of trucks and they might have been behind the seat. I don't really know that much about those trucks, but I do remember them being inside the cab into the 60's, standing up behind the seat.
