not sure about the zillas but i am running 28" outlaws but need wheel spacers or rims just got back from my first ride with them and they were unbelievable
Anything bigger than the stock tires on the stock rims and you will probably need spacers. If you're going to aftermarket rims, the sky is the limit for size. Clutch kit would be nice if you go 28 or larger, but if you run low range when required, you'll be fine. I have 30's on mine...no lift kit.