I'm still running the 3.91s at this point. Be I've got an offer to trade a 2.76 sure grip for my 3.91 but I'm the fence about loosing my low end grunt. Oh decisions decisions.
Don't trade ... buy the 2.76 from him or get a 2.76 open diff cheap somewhere
keep the 3.91 and swap when you fell like playing with the stump puller gears for a while then swap back.
Pretty easy with 8 3/4 rears and doesn't really take to long