Probably a dumb question, but did you manage to mount the shocks upside down? I cured a bad-handling pure stock race car's problems by simply installing the shocks the right way. The car builder used a set of load-levelers, and mounted them the way they bolted on the easiest, which put the fluid reservoir on the top.
Jerry
Here are a couple of pics of the rear shocks/springs. Let me know if you see anything blatenly obvious.
Pic 1 Pic 2 Tires are radial, by the way.
