depends on how much you build the axles. i know several people with fully built toyota axles running 42's. to run really any tire larger than a 33 with a locked front diff, these parts will eventually become necessary as you destroy all the stock stuff: longfield 30 spliners, longfield hub gears, ARP hub studs and possibly the 6-pin hub upgrade, ARP knuckle studs/ trail gear 6 stud knuckles and steering arms, a good locker (the lunchbox style, though a great option for most rigs, wont hold to 42s in my opinion), a high pinion 3rd member.
and after all that you're just gonna blow ring gears... but people somehow do it anyway. far more people run 40s on built toy axles. still.. this size is pushing the limit.
36/37s with a built front end and a light right foot is nearly foolproof. go for it.:awesomework: