I posted this link in the last conversation we had about custom spring rates. Check out the install:
http://www.240sx.org/links/installs/...ng_choice.html
also, I have done a fair amount of calculations and if you have ridden in a car and you like the spring rate they have, I can tell you what would be equivalent in your car.
check out the other thread about a week ago that talks about custom rates in ground controls.