As far as the rear tire size, to me it depends on what kind of terrain you're in, as in what would be hitting your skid plate with 20" tires. Rocks tend to do a lot of damage, so in that case maybe 22s, but other than that, just get 20s. Big tires suck horsepower, and they don't bite as well as smaller tires. Get 9" rims though, and 21" tires up front.