got my coilovers but have questions

ok i just got my ground pounder coilover kit and put them on my new KYB GR-2 struts. i am alsio installing a bbk camber kit.....but i have a question

the springs that came with the coil over kit are 400lb springs...is that really stiff? my rear suspension consisits of lakewood 50/50 shocks and goldline progressive

springs
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I think the 250's are street springs and the 300's are supposed to be real stiff (bit less than a FMS c spring) so those 400's are probably going to be like rocks.

Does this car see any street action? If so, I would probably recommend getting something lighter. For drag racing, they should be fine