Back around 1973 or '74, I had a basic 1970 D-100. V-8 and 3 on the tree. I used to load it until it was sitting on the bump stops. I later added some booster springs that were mounted on clamps around the axle housing. I still loaded it to the bump stops. I'm surprised I didn't snap an axle. I've seen pickups where that happened. You can tell a truck that has had that happen by the rear quarter panel.being folded under behind the rear wheel.