This truck looks like a 1-ton to me. The front wheel openings look small, like the 1/2- and 3/4-ton, and those wheels look like the 18's used on the dually 1-ton. The wheels are 8-lug, versus the 5/10 lug wheels on the bigger trucks. The wheelbase would be the same as the short 1.5-ton (137"). The front bumper is also the 1-ton style, similar to the smaller trucks.
Are those the lever-type door handles? If so, this would be a '51. The Chevrolet script on the side of the hood, possibly missing the series number under it, also suggests '51, as they used only the series number designation in '53, without the Chevrolet (unless the Canadians did it differently).
