well its all depending on how low you wanna go. you can just do a flip kit in the rear and it will drop it 4-5 inches. in the front you have to use lowering i beams . which will drop it 3-4 inches in the front. .
now for a more major drop i would just swap out the lief springs in the back with a triangulated 4 link. thats what i did on my 88 . now you will have to have some kind of coil springs or air bags or hyraulics on ther to hold the truck up. i got my 4 link from fender bender interational. it comes with everything you need. except a monster knotch kit. which i just made mine out of some box steel. i can take some pics if needed to see how i have installed mine. hopefully this will help you out i would also recommend to replace the transmission crossmemeber and the i beam crossmemeber to give you more crearance