OK, first off I'm no suspension expert but just the same I'll through some ideas out there. This is just a guess at the numbers here so bear with me. Lets say you have 600 lbs. springs on the front and lets also say the distance between the pivot points (A arm mounting and spindle mounting) is 14". With the spring (which can be seen as a pivot point in a basic lever) in the center of this distance. If a 600 lbs spring is compressed 1.5" it has a load of 900 lbs. acting on it. So if a normal load compresses the spring 1.5" and this equals 3 " change at the tire then reducing distance on one side of the lever will change the balance point of the lever (the spring) from a ratio of 1:1 to a ratio of .714:1 so now it will take 1260 lbs of force acting on the tire to compress that spring 1.5". Because your truck still weighs the same it will rise by .85" this in turn change the alignment for sure. I'm thinking you may need to cut the coils by 3/4 of a coil each to maintain the same ride height and you will still get a stiffer ride. Of course all this is based on my guesses on measurements.
Boy this chit will make your head spin
Rob