12" and believe me you need them. I'm very unhappy with the front shackle angle though; so I'm about to remove the top two leafs and replace them with the top two from my rear pack, add a drop hanger, and redrill the shackle 1" shorter. That should also help with the really steep front driveshaft angle. Using a drop drag link for steering as of now. I will upgrade to highsteer as money allows. I also suggest redrilling your spring perch to move your axle 1" forward. You'll need all the firewall clearance you can get at full stuff.
For the rear I used 89-95 rear springs and a 6" shackle (bought a long one so I can redrill if I need to). I had to move the rear hanger (no biggie) back 2.5". I can tell these springs are for a little heavier truck, but I also dont have a rear bumper, tailgate, or spare. They flex pretty well when the weight shifts back there. I triangulated 12" shocks in the rear. Like this: /\. And installed a u-bolt flip kit.
Oh, and I built a square front D-shaft yesterday. The 1" forward axle and extra travel popped the stock one right out.
That's about all I got. Good luck and don't be afraid to attack that front axle with a cut off wheel or torch. I cut off the sway bar tabs and that panhard bracket thingy. While you've got the axle out, go ahead and fab up some knuckle ball gussets and gusset your steering stops. I forgot to and now I'm having to grind off new paint and weld under the truck upside down. No bueno.
Gonna be getting 5.29s and 35s as soon as I can afford them.
