they are arched differently as well , the idea is to put the stiffer /taller spring on the passenger /torque side of the car so the car will launch straight , as others have said swap them for some stock or xhd springs if you want to level the car .
Except that I just put some heavy duty springs on mine (from Springs N THings online) and the driver side is nearly 3/4" lower. Then I sit in the car and I'm sure its probably 1 1/2" lower on left side. I'm pissed about it, havent contacted them yet...