im running 39.5 iroks.  I've got 30 spline longs and his hub gears, tg's trunnion eliminator and stock dual transfers.  4.7s in the rear case would be nice.  but i havent broke anything yet.  i dont drive like a retard either tho...

edit:
I went from 37s to the 39.5s as well.  if you plan on driving it on the street then stick with the 37s.  I've about decided to make mine a trailer only rig.