A friend of mine had a set of 100 # springs we put on my coilovers. Measured height before and after. Took the difference times 2 times 100. I believe with mine they compressed 6 inches. So 6x2=12, 12x100=1200#. As far as what springs to get I called Wayne Israelsen at Alltech motorsports and told him what I had and he came up with a PAC spring package. In my case the coil was compressed the same on each side. If it is different let Wayne know.His prices on springs are as good or better as anybody out there and he knows what he is doing. This way I didn't have to worry about weighing the axle then subtracting that weight. Keep in mind this is what I used for a trail rig and it worked well. If you plan on racing you may want to get a little more precise.