Jack, I put a set of these on my truck to get rid of the overload slap.
http://www.oreillyauto.com/site/c/detail/SPP0/21080.oap?ck=Search_21080_-1_2797&keyword=21080
They worked well, and lasted about two years. SPC was sending them out with catalogs a while ago, because they couldn't figure out how to sell them. Call their customer service line and ask if they still are. If so, request a catalog and you get a set for free.
MA sells a similar product that's just a huge o-ring and not really shaped to fit the spring, but I've heard they also work.
I'm about to head to the junkyard and scout for some decent rear springs. Time to ditch the air bags.
BTW, my CCSB has a 1pc aluminum driveshaft. No clunk, original U-joints still tight and not squeaking. 220k miles and counting...