For you with plowing in mind I think I would go with a detroit out back, trutrac up front and either 4.88s or 5.29s. If you still really want to run 31s then 4.88s, if you will stay more 33s and up then 5.29s.
I wouldn't discount thinking about an aussie locker in the rear though, they are vastly superior to other lunchbox and we have 3 running in rigs right now holding up well to all kinds of abuse, towing and 35" tires. Also my aussies have always been even smoother than the detroits I have ran.
Of course you can't go wrong with a detroit anyway...