There are a lot of different model numbers for 1939 "trucks" as there are different types of trucks, various lengths of frames and different engines - all having different model numbers. Assuming ActionYobbo has the 85 HP engine in his 1 Ton truck, then the correct model number is 91Y.
The 1 Ton truck fits between the commercial (pickup) and the regular truck (1 1/2 ton). All share some parts and all have unique parts so it's important to keep the model number straight when searching for parts.
The 1939 1 ton truck with the 85 HP engine is Model 91Y and with the 95 HP engine 99Y and the 60 HP engine model number is 92Y.
The 1939 regular truck with the 85 HP engine is Model 91T (134" WB), 917T (137" WB), 911T (191" WB) and with the 95 HP engine 99T (134" WB), 997T (157" WB), 991T (191" WB).