You should be ok with 4.10's if your planning to stay with the 31's but if you plan on running bigger then you should go with 4.56's. Best to get the gears and whatever locker you run with at the same time so you won't have to pay twice the labor. I run a detroit in mine and pretty happy with it, I'm running 4.56's in my rig but I'm running 33's

 

I've installed all three.
Powertrax NoSlip FTW.
Fit and finish are better than the Aussie and the Lock-Right. Basically you get what you pay for.

 

Weld it.... free and works great