I have built a few packs over the years using Chevy Springs(the non-63" packs). I usually use the Chevy main o under the Toyota main, then another Chevy, then Toy, Toy. Each of the Chevy Springs can yield 1-2" of lift plus the thickness of the spring itself(3/8") depending on ho much weight you are carrying. If you don't carry a shell, or a lot of weight in the bed, the Chevy main(cut to fit between the Toyota main and 1st leaf down from main, should give you about 2" of lift w/o stiffening the ride. You will need to get new center spring pin bolts, and if your U-bolts are the original ones you will want to pick up a new ones. The oem stock u-bolts are usually good for one additional spring sometimes two, but the center pin usually can't be re-used.
