I have talked with eibach before, as well as my suspension/ chassis engineer buddy who agrees. good point on H&R, Bilstien... I wonder if they suggest springs to use with there setup...?
+1 for maximum motorsports, stay away from kyb they barley pass as a stock replacment not nearly enough dampening on a lowered car, i have a mm coil over kit with bilstiens and love it, but it was pricey(1600), i also have heard that the bullit kit really does not work on a fox
It depends where you purchase the parts from as sometimes parts are mixed and matched and you could end up with 01 Cobra or 03/04 Mach 1 parts mixed in. I have the Actual 01 Bullitt Parts on my GT and it worked out Fantastic, it lowered the Front about 7/8" and out back around 3/4", the ride and handling are superior compared to stock!
I have the Bilstein HD's and they ride awesome... I'm on stock springs trimmed 1 coil in the front (about 1.5" lower and stiffer than stock). According to Maximum Motorsports the Bilsteins are compatible with anything from stock springs to a high rate lowering spring.