The rear shocks mount to a bracket bolted to the frame and can be a source of failure largely do to the bolts. The upgrade uses a far sturdier bracket with more/better hardwear.
It is fairly inexpensive and a straight forward replacement, did mine last summer,couple hours with handtools. At the same time I used it as an oppurtunity to bolt shoulder harness' into the frame since the locations are a couple inches from the new mounts.
You probably would benefit from membership in the SPF owners group which is cheap and has lots of technical articles as well as all the upgrade data with how to stuff apleanty.
http://performanceunlimited.com/cobr...ion/img159.jpg