Travis,
Sorry about misinforming you earlier about the axle... It's been awhile since I had a Yota here. I totally spaced it.... Here is what a front Yota axle would look like:
As far as being nervious about the stock axles with 5:13's it will totally depend on your driving habits and a bit of luck. If you wheel it hard then at some point most likely it will break. But that can be said about 31's too. The likelyhood does increase though due to the size and weight though on a bigger tire.
I have 9.5x34 TSL's on aluminum rims. They are tall, narrow, and light. They weigh less than my old 30x9.5 on steel rims. The tread width will cut through the mud and is light enuff to float higher in soupey stuff.
I ran them for 2yrs on stock gears before changing to 5:13's and another year before installing 6:5:1 transfercase gears.
Most of my driving is daily around town and only on occasion do I have time to go wheeling. No rock crawling, mostly muddy logging trails, creekbeds, and washouts.
I am building it to do just that kind of mutipurpose fun.
I am not saying your set up won't break but I am saying alot depends on what you want out of it.
My theory is get as close to what you want as you can and buy the stuff you need as you go along or when it breaks then make an upgrade.
Hope that makes better sense... Good Luck!!!