What does he want to do with it? Going camping? Desert racing? Rock crawling?
There's a lot of aftermarket options from lots of vendors.
Biggest issue I have in mine as far as going to bigger tires is gearing. I have 33 and 34" tire sets. 3.73 diffs are okay stock but not really great of bigger tires. The next ratio is 4.56 and with the 5at that's pretty low for highway speed. I've had a conversation with circle k about making 4.10 ratio gears. They'll do it, but I'd have to order 200 sets and I don't really have a use for that many. Price is actually pretty low though because they can cut them from existing forge blanks that they already make for the 4.56 ratio. Really just need a gear vendor to get on board with it to sell the 4.10 ratio. I re geared to 4.56 and then went back to 3.73. I spend most of the miles on pavement and the mpg hit from 4.56 was just too much.