you need lengthened wheel studs if your shims/spacers are thick enough... you need at least SIX full turns of lug nut engagment, at least thats what i recall the NHRA saftey inspection stipulations. anything more than that is gravey.

just make sure your wheels dont stick out TOO far past the hub mating face on the rotors..

and if you put htem behind your rotors, your brake caliper travel will be messed up. put them between the wheel and the rotors.