I must have said it here 20 times:
Gears don't make power! In fact, if you want to get technical about it, they make slightly less power.
I have also said this numerous times: Torque is not power. You can have 1,000 ft/lbs of torque of and 0 power out put.
Put a set of 3.00 in you truck and chassis dyno it. Then put a set of 4.56's in and dyno it. Want to bet me a $100 bucks which gear set puts out the most power to the rear wheels? :B
To much work for you? Fine, just dyno your truck in 1st gear and then dyno your truck in 4th gear or whatever gear is closest to a 1 to 1 ratio. What puts out the most power to the rear wheels?