I'll have to amend my first post, it almost certainly has to be a 1940 model. In 1941 the headlamps were moved to the CENTER of the front fenders and mounted in "pockets" formed in the top of the fenders. This truck does NOT have that, the headlamps are more on the INSIDE of the front fenders.
Also, the cab windows do not have "vent wings", they are all one piece of glass. The vent wings came about later in the '40's, maybe right after the war?
The four "ridges" in the lower rear part of the front fenders were started in 1939, plus this style of grill is '39 thru '47. Pre '39 grill was entirely different.
And of course, no new trucks were built during the war for civilian use so that eliminates '43, '44, and '45 models.
So we've narrowed it down to a '39 or '40. Now, the big difference between '39 and '40 was the shape of the chrome cross on the grille. In '39 and '40 the vertical bar was the same, however the horizontal chrome bar changed from '39 to '40. In '39 the horizontal bar had an upward sweeping angle to it as it went outward to the fenders. In '40 this horizontal chrome bar became straight across to the fenders as your truck has.
My conclusion: Your truck is a 1940 model. (just my uneducated guess)