Gear question??
It depends on what size tires you'll run.
With 9" of lift you have plenty of room to run 42s without much problems, other than the 1/2 ton axles wanting to blow.
If you go with 4.56 gears, tires could be anywhere from 35-38s with that transmission, but if you want to run bigger, then you might want to try and get some 1 ton axles and regear them instead of upgradeing the 1/2 tons that couldn't handle a tire over 38s to good to start with.
this is commonly done is mud boggers to turn the front and rear tires at different speeds, with the fronts spinning a little faster, but if you are going to be driving on hard pack, the difference will give you bad axle bind, and cause eventual transfer case failure, or other drive line problems and failures.
you can run the 4.88 in the rear and the 4.56 in the front on the road or off road on hard pack, but you will have to compensate for the different gear ratios with different size tires front and rear.



