old post...but check out Timbren http://www.timbren.com/ They make rubber springs to replace the factory bump stops. I have them on my Astro...takes anywhere from 10-45 minutes to install depending on vehicle. They cost about $180/pair for the Astro. The fronts added 1500 lbs and the rears 2000lbs, but you don't want to exceed the gross axle weight. They're basically passive helper springs. Here is the pdf file for the install on the TC http://www.timbren.com/timbren-application-guides/application-pdfs/FRTC.pdf
