And aleej..... to explain further why we're steering you away from 4" shackles:
I was the one that worked with the tech team at Warrior when the shackles were designed and engineered for the first production run.
http://explorerforum.com/forums/showthread.php?t=13143
There were specific reasons that the shackles ended up being the dimensions that they are. In addition to what has already been mentioned, there is a point of diminishing returns when going up in shackle length. The bottom of the shackle is bolted onto the rear of the leaf in a free-swinging hinge arrangement. Once the shackle length gets longer, very little extra lift is attained because the leaf does not hold its original curve, but rather starts flattening out and pushing the shackle back. Test this by lifting your rear tire off the ground, putting a jackstand under your frame, then using another jack to raise and lower your rear tire. You'll see the leaf arching and flattening while the shackle swings back and forth.
When you go to a longer shackle most of what will happen is just that, and you'll not end up with much (if any) more lift. The Warriors are as long as you can go without hitting that threshold of diminishing returns.
The Warriors aren't 4"; but are still probably 3" longer than yours and will give you about 1.5" lift. To get the rest, install add-a-leafs, or check the sticky at the top of this forum on how to take an old F150 leaf spring from a junkyard and use it in your existing leafpack to finish the lift.
Hope that helps make it a little clearer for you; we're just trying to help you avoid mistakes we've all already made/been there done that/etc. There's no use in others like you wasting money, time, and effort to learn the same thing we already have.