Information here might be of use. Keep in mind, although it says g37/g35, the 370z uses the exact same bars. In fact, from my conversation with eibach, the OE numbers were not taken from a g35/g37, but from a 370z. Enjoy
Eibach Springs : NEWS : INFINITI G35, G37 2007-11
http://performance-suspension.eibach...g35g37_ark.pdf