I agree with Jason, the leaf packs are the way to go. There are a few ways to go with this.
F-150 leaf packs from a Junkyard for lift.
Custom made leaf packs from Deaver, EMU, etc...$$$$!!!
Add-a-leaf/helper leaf for cheap (stiffens ride but gives a little lift).
Add a 5th leaf from another set of stock leaf packs, cutting off a few inches and placing under longest spring. Maniak Mod.
Having a new leaf made & added, and have the stock pack re-arched for more lift, what I did. I have a 5 leaf pack and I have 4" of lift over stock specs from it. I use the stock shackles so it does not hang down(hang up) and prematurely wear out the leafs. This was 3 times the cost of shackles, but worth it to me in the long run. But I take my rig off road.
Its up to you. Shackles vs leaf mods. Shackles work great for a cheap lift and street use. Leafs work better for off road.