First, I would dump the 4x4 and get a locker/lsd instead. Lots cheaper, better gas milleage, and better traction, UNLESS you have a 4x4 with a locker.
I had a '97 f150, it was a prety good truck, five speed and v6. Beat it like a dog. Had to redo the heads and gaskets, lost the crank pulley and...