I agree about the camber adjustment kits 100%, and to also add, when you lower these cars, it's imperative you replace the stock shocks and switch to a performace gas shock like Tokico. The stock shocks will not handle the added pressure and your car will continue to drop and will become bouncy and won't be safe or sport-like feel. Stiffin it up with gas performance shocks!

later...

 

The hotchkis springs are very close to stock rates. For the Z, it's stiffened by 10% at the front whereas the rear is softened by 7% or so... I don't know about the G35c springs though.

I don't plan to change my shocks until they're worn, and I figure with such minor changes to the spring rates, it won't affect the shocks too much.

 

Well I have the Eibach prokit spring setup. I've had them on for over a year now and it continues to drop. Hell, I can't even pull into Kwik Kar anymore to do an oil change w/o the guys pulling up the front to give me clearance. Trust me, once you drop it, you'll continue to sag as time goes on, the stock shocks have a hell of a time dealing with the added pressure and don't perform as they once did. You can wait like I did, but you'll really benefit from performance shocks (like Tokico)....hella difference, not even the same car!!