Re: gear ratio
well with a truck that size, you can go as big as you want. But remember...
Both the front and rear need to be changed. other wise you will fry an expensive drive train component.
The bigger the gear ratio (i.e. 4.10-4.56-5.38) the more torque and worse gas mileage and top speed. it all depends on which motor you have and what tire size.
You must reprogram the computer to adjust the speed sensor for any such change, especially if you have an automatic trans.