The three ton I don’t know about, but the 1 ½ ton and two ton taskforce trucks have the same sheet metal.
The difference between the big trucks 1 ½ and two ton from the ½ to 1 ton is in the grill and fenders. The core support, hood and cabs are the same between the small and big trucks.
In the big trucks the grill opening is wider and taller and the head light are set further apart as well. The fenders also have a bulge to their sides adding to the width as well as just being a bigger opening.
There was also a change to the fenders on the big trucks in 57. On 57 to 59 the wheel well opening was moved forward for more tire clearance at the floor board. There was only two changes to the suspension with this change in sheet metal. This was to the front springs and the drag link, the axle locating pin was offset forward and the drag link was lengthened moving the axle forward.
Hope this info helps.
