with the torsion bars crawl under the door area of your rig and you will see the back end of the torsion bars. they're about 1" in diameter and run from the front wheel to a frame mount there under the door (one on driver's side and one on passanger side). on the frame mount you will see a verticle bolt that goes through the torsion bar key (its a metal bracket attatched to the rear end of the torsion bar inside of the frame bracket). tighten that bolt up an equal amount on both sides (if you tighten the drivers side up 3 complete turns, do the same on the passanger side or else you can create body lean and throw your front wheels out of alignment).
with the rear add-a-leafs i cant think of the brand i'm using (i got mine used) but make sure that you get the long thin leafs because they will allow the spring pack to flex. stay away from the short thick add-a-leafs, they limit your articualtion for the springs.
adding a locker requires removing the 3rd member from the axle housing, fairly involved and not the easiest thing to accomplish if your not familiar with axle work. can be done though.