The 1.5" replacement coil springs are used to help level-off the factory "nose-down" stance, or to offset the weight of a winch or snow plow.  Note that lift height is compared to "new" condition factory coils; most factory springs have sagged somewhat so expect slighty more lift.  Caster angle is affected, although generally now enough to impact driveability.  Regardless, we do recommend upgrading to Urethane track bar and C-bushings, and replacing the shock absorbers; all are available from Superlift.  

If rear lift is desired, opt for a Superlift block kit or add-a-leafs.