I just went through a similar scenario. I eliminated the top pad (between perch and spring), installed 1" lowering blocks from Guldstrand on top of each leaf pack, and reused the lower pad between the shock mount and leaf pack. When I mocked everything up, for whatever reason, the RH pad didn't want to sit flat against the spring. I set the car up on corner scales and played around with shims until the cross weights were close. But I digress...
Here's my suggestion: if you don't want to cut one of the existing perches off and properly reinstall it so it's correctly positioned, measure how far it's rotated and use one of these between the spring and perch:
http://www.speedwaymotors.com/xq/asp...qx/Product.htm
Hope this helps.