LSx 454 and Supercharger ... what coilover spring rates ???

I'm purchasing a set of coil-overs and need some advice on spring rates from other members who have ran a heavier iron block in a C5/C6 chassis.

2003 Z06 C5
Iron LSx454
A&A supercharger kit

*****WHAT SPRING RATES WOULD YOU RECOMMEND??????
The iron LSx 454 block and supercharger kit is adding approximately 250 lbs to the front. I WANT TO BE AT FACTORY RIDE HEIGHT in the front/rear with a coil over kit.

*I currently just tried 600 lbs front springs and 550 lbs rear springs.... and it sits too low in the front and too high in the rear.