Well I don't know about 30" I put 27"Zillas on my 500 rubicon and find it perfect I put 7psi in them for a good ride and the measure just over 26 1/4 inches.
The Rubi's got way more torque than a Rancher plus it has a high/low range which the Rancher does not. Going to a 30" Zilla means he also has to go with 14" rims and all that will add up in extra weight and rob him of power. The Rancher is meant to be a trail machine, if you want one for mud then mods are needed to turn aggressive mud tires.