Does anyone know of a company that will make custom springs with the specs that you want?

Looking for springs with rates close to the NISMO s-tune, but linear. I have seen the Cobb springs but they lower the rear more then the front. I want same drop in front and rear or slightly lower in front.

 

Hyper Coil, Swift, and I think Eibach.

 

Eibach ESS for the rear. The front is where it gets interesting. Get a set of pillowball mounts and some hardware from truechoice to run 2.5" springs with a coilover sleeve. I imagine this will add up to less than custom springs. But anyway find the correct eibach ESS 5"x11" springs for the rear and then just buy a full set for the front springs. Reality of the question you asked is you haven't done your homework

 

Buy the Cobb springs.

According to Cobb's web site they drop the car 3/4" front and and 15/16" rear. Meaning the rear is only 1/16" lower then the front.

In this thread, someone measured them for spring rate and got 426/535
https://my350z.com/forum/brakes-susp...ng-anyone.html

The way I see it, you found the linear springs you wanted in the Cobb springs and they are close to the S-tune rates. Their are other way's to do what you want, given how close the Cobb product is to what you want, that would be beyond pointless. And honestly, it's supper easy to make yourself a simple shim to install above the oem rear upper spring seat to gain rear ride height. I've made them myself from 1/8" thick to a little over a half inch thick.