I have Ford keys up front and added these in the back, I'm about 1.5" over stock now.

http://www.supersprings.com/productguide.asp


Pic of my truck's stance
http://www.public.asu.edu/~cwessel/IMG_0670.jpg

 

Depending on how old/worn out the truck is determines the necessity for Ford keys... older NBS trucks with miles will need the keys and maybe 1 ton bars to get level while a newer '06 or '07 Classic model can get level using the factory keys. A buddy of mine put Ford keys on his BN '06 Z71 and was confused why he was hitting the upper A-arm limiters with the bolts backed all the way out...the reason being his factory bars were BN and more than capable of leveling the truck. IMO, only get the keys if you can't level your truck with the stockers.