on that truck i'd run a bell tech or djm kit. 2" spindles 3" coils and flip kit in the rear with a shackle. The shackle will be adjustable for 1 or 2" of drop. set it at 1" if you decide you want it lower move it to the 2" hole and cut 1/2 of 1 coil off the spring. 5/7 is usually the max for everday driving (non towing) 4/6 for towing. This also depends on your wheel/tire size to make sure you have turning clearance.
Let me know if you have any questions i can set you up with the parts you need.