Jackyl-The front of the frame on the 1 ton is 1/8" wider than the 1/2 ton. I don't know if the 1/2 ton front springs are going to fit the 1 ton frame. The 1/2 ton springs are 38" long. the 1 ton springs are 40" long. So you'll have to relocate the spring mounts. The rear springs differ in length also. The 1/2 ton rears are 54" and the 1 ton rears are 46". The 1/2 ton rear springs won't fit in the 1 ton spring hangers.
The 1/2 ton springs are narrower. Also remember the 1 ton axle mounts under the spring, the frame is flat over the axle with no clearance hump like on the 1/2 ton. Why are you concerned about the weight of the truck? Are you getting rid of weight for some reason? That El Camino axle will be fine with the 3.42 gears. That axle isn't effected by the weight of the truck unless you try to carry 2,000+lb. load.
