My sugestion is going to be slightly diferent. Since the rear springs are already sagged down about 2-3 inchs just from the weight of the truck and cargo, I would attack this from a completely diferent angle, that is going to be easier on you, and your truck. What I would do is contact a trailer suspension place or dealer, and see if theres a way to install airbags ontop of the axle, and have the counter part mounted to the frame or frame rails of the truck. Have a simple switch inside the truck that you can flip, that will raise the truck, buy filling up the air bags, when you get to your dock. These air bags are actually going to serve a dual purpose. Instead of the 8000 lbs of a forklift going into your truck, and flatening your springs, the majority of the weight is going to be held buy the air bags, thereby giving a longer life to the springs of the truck. And the fact that this setup will add maybe a total of 50-100 lbs to the weight of your truck, it means you wont have to be concerned about the GVWR being exceeded. I think thats the term I am looking for? Also you wont have to be hassled by getting out of your truck and cranking down some landing gear to raise your truck up, or getting out some ramps to drive your truck up on. You simply back into the dock, hit the switch, get unloaded, hit the switch again, drive away.. Its simple, light to the truck, and probly could be retrofitted onto the truck fairly easily..