This generation of GM 1500 series trucks is the first to use a front strut suspension. The strut holds the coil spring on both 2WD and 4WD trucks so that means that in addition to lowering them with a coil or knuckle you can also lower them with a strut that has the coil mount relocated. In fact, BellTech struts come with spacers so that you can set your ride height from a 2 inch lower right up to a 2 inch lift. The advantage of this is that you aren't change the coil and firming up the ride and the struts are relatively cheap. My 2 cents still says that the knuckle is the best way to go. BellTech also has a knuckle designed to correct the suspension geometry when lowering more than 2 inches. Look for part number 2511. The 2WD and 4WD trucks take the same parts in the front but use caution when lowering a 4WD more than 2 inches because it can cause early drive axle failure.
In the rear the front hangers are all welded on so if you want more than a 3" drop (Shackle and remove the factory block) then you need to use a flip kit. Flips are available with 4 to 7 inches of drop to achieve your desired stance. If lowering more than 5 inches you need to replace the rear shocks.