That model number sounds Canadian and since you are in Canada I imagine the truck was made and labeled there.
All of that to say the usual US based model identification isn't going to work on that truck. I guessing from the 4's that it is a 4000 series truck, which would be a 1-1/2 ton. Judging from the pictures it looks like the shorter wheelbase, which would be US model 4100.
IF I'm right, the wheelbase would be 137 inches. And if that is the case the bed from a 1-ton would be the right length. The fenders are not likely to be large or wide enough, but it might come close...
