I have 20 inch rims with a 35mm offset on my G35 sedan NON sport suspension, if I lower with Eibach Pro Kit or 350Z springs will it rub?

 

The diameter is not so much the issue, it's the width. How wide are the wheels and what size tires are you running?

 

They are 20 x 8.5 and the tires are 245/35/20 all around and this is on a regular sedan suspension

 

There are a few people that have 8.5" wide wheels with the +35mm offset. They claim there is no rubbing. You will be cutting it close, but you should be OK.

If you do rub it will be on the small inner fender lip. This can be successfully rolled or cut to aleviate the problem.