I just finished a test of .5" taller upper and lower ball joints. These are made by Power Performance Motorsports for 2nd gen Camaro/Firebird.
They make impressive gains in neg camber, the upper being the most beneficial with very low impact on bumpsteer. The tall lowers add a little more, but bumpsteer is worse. The 2nd gen steering linkage can be moved around quite a bit to improve bumpteer and even with tall upper and lower balljoints our early runs with the test car do not produce any noticeable steering feel problems.
David
Link:
http://www.pozziracing.com/second_ge...o_tall_bal.htm
Chart: