Thanks for the additional information. Most of the MII kits are pretty well thought out and, while I am sure the installation can get screwed up, install pretty easily. Sounds like the PO did not even have a shade tree to work under if he messed things up that badly. Could you send me a pic or two via email of the current set up? This is an area I have become fairly understanding of through my own trials.
Sub-framing may be the least costly to perform if you are doing the work yourself. If you are having a shop do it it will probably wind up being close to a new MII set up. Before you do the sub-frame, become as familar as you can with the process. Check out the Bobcoauto.com site. It shows how the f-body sub-frame is mounted to an F100. The process is very close to the chevy install. This link also shows the process although for a car. Process is the same.
http://www.hotrod.com/howto/42838/ RBs is
http://www.rbsauto.com/ As for the rear suspension you might consider a spring set from
http://www.classicperform.com/ or
chassis engineering.
Good luck.
