If you're not planning to place big loads in the back removing a couple of leafs will probably do the trick for you. You can do this yourself so the only cost is your time. You can also trim the removed leaf(s) and place them on top of the spring pack for additional drop. The advantage of removed leafs is a much softer ride.

There's some do-it-yourself dearching described over on that other hot rod board. With dearching, most of the original load carrying capability will be retained.