You don't need new leaf packs unless you're planning on doing some real crazy off-roading, but if you are going for a 3" lift all the way around, you will need a 3" block. This will give you roughly the same setup as our 5.0L Project Truck, though we only have our fronts set at about 2-3/4" rather than the full 3" that the coilovers are capable of.