I have the Kore HD leveling kit: two coils, billet blocks for the front sway bar, Bilsteen(sp?) shocks, and new bump stops. Easy to install, and a firm but not harsh ride. About 6 bills from DRC; good shop to deal with. I haul a Lance 1161 camper with no ill effects. Haven't made the long haul yet. Looking forward to the trip.
There are many options from many vendors available. Depending on what your intentions are with your truck, pick the kit that meets your needs and fits your budget.
BF