Again, I am not an expert but I have been told that the cabs are the same on the 1/2 ton and 2 ton. However, the hood, grill and front fenders are much larger on the 2T.
I don't think Chevy made a box (we call them beds in Texas) for anything larger than a 1T. I doubt if it would look right proportionally.
If you don't want the grain bed, a stakebed would look good, and allow you to carry some things.
EDIT: I was looking for a picture of a stakebed in the gallery, and noticed several trucks that were model 4400. Is that the number you read instead of 1400? If so, it appears the 4400s were 1.5 tons, the 6400 were the 2T.
