will 315/70R17 kumho mt kl71 rub on a fx4 with a 2.5" level on rims with a +15 mm offset? if so what can be done to fix it and is it worth it?

 

That's basically a 35x12.50 tire. A 4WD with a 2.5" leveling kit should be able to handle that. What is the width and backspacing for the wheel you are considering?

 

the wheel is 9in with a 5in and change backspaceing

 

You should be fine.

 

I had a little rubbing on the lower wheelwells when turning even after trimming when I had my tires on 17x9 with 5" BS wheels. They have to be on stock wheels or ones with close to stock specs. If you don't mind a little cutting and hammering you may get them to work. I ran mine for 4k miles and the minor rubbing drove me crazy. Offroad is worse. Just my 2 cent's.