BBM --- yes, the diameter of the pistons was the main issue that was said to be the differing factor.

I don't know how much it really makes any difference.... say from using the Wilwoods with the adapters avlbl from AREng'g.

Mopar Mitch "Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers! Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!