I am picking up a NISMO S-Tune sus from a 350Z. I know it is compatible but how much lower will this make my car?? 1/2 inch more than the Z??

 

I think that's right. If memory serves, it keeps the same ride height on the Z which would equate to ~1/2" drop on a G35 Coupe, a little more on the Sedan.

 

The stock 350Z springs will lower a G35 1/2" The 350Z Nismo springs are designed to lower a stock 350Z 3/4". One could assume that the total drop would be 1 1/4" However the true drop is around 3/4" to 1" and you will need camber kits for the front and rear to allow for a proper alignment.

The spring length difference between a 350Z and G35 Nismo S-tune spring is around 15 mm if memory serves me correctly. I'd have to look up my notes to be 100% certain.