Do some looking but I just had a friend tell me about MCE flat flexible fenders and from what I've read you can run 35's without lift and without rubbing.... If that's an option.

 

You will not gain just running rubi coils, you need to compare the spring numbers and since you have a JKU don't expect much and really I would not waste the time to swap. Note the bottom of my signature.

 

Hopefully this will help you. I am running 33x12.50 cooper stt on 15x8 wheels with 3.75 inch backspacing. The pics below show this setup before and after installing a 2.5 TF coil lift. I could get away with very mild flexing while connected before the lift, but couldn't go over a pot hole disconnected without rubbing like crazy.

Muddy pics are before lift. Clean pics are after lift.