You could remove the rear spacer blocks between the springs and axle they are 4 to 5 inches, assuming you have a 4x4. If that is to much then you could get a set of spacer blocks from a wrecker's and have them milled down to the thickness you want. If you have access to a band saw and angle grinder you could likely do it yourself or get it close so it would'nt take a machine shop long to finish off and get true and parallel. You would likely need to shorten and cut a few more threads on the U-bolts.
If you don't need the carrying cap. you remove a few leafs out of the spring pack.