for the rear, i think you have to get longer shackles, but not too long because you could hit the bottom of the bed. you don't want shorter ones or it lifts your truck since the shackles are above the cradles. for the front, i bet you have to get modified hub assemblies with the bearing hub mounts higher on the assembly so it lowers the truck. at a certain point, you will have to get into serious mods to lower it though
but, a few people have done it so they should come on and help out.
but, a few people have done it so they should come on and help out.