Ok thanks, I did have a sheet from somewhere which calculated rates of around 300lb front and rear as a starting point but I think the sportlines I have are higher than this.
Springs front 160- 239 lb/in progressive
Rear 354- 752 lb/in progressive
from kam racings site which would say the rears at 300 are way too soft.
It all depends on what you use the car for really. If you go to stiff at the rear and the car gets used on the road it will swap ends quicker than the blink of an eye and you'd need to wear a gum shield when you drive it! Lol!
It's worth keeping in mind the lever ratio of the rear axle as well. I think it's 1.74:1 but I can't 100% be definite. 500lb rear springs are nearer what you want for sprinting, but keep in mind the lever ratio as that affects what spring rate the wheels "see's" and also the rear dampers will need revalving to suit.
350 - 450lbs fronts aren't to bad either.
What set up are you running? As in dampers?