4wd shackle NBS

Hey so im 2 inches lower in the rear and trying to figure out what i can do to raise it up a little in the back, i found these shackeles on a web site any one ever try them, i thought you can't do shackle lifts on nbs trucks let me kno here is the link to.

http://www.airbagit-store.com/product.asp?returnURL=default.asp&ID=99553