How tall are your tires? The truck should accelerate faster w/ the lower gears, the effect is similar to putting shorter tires on it w/ your current gears.

 

I have 31.5's. I think 4.10's would be more what I would need. I tried cruising down the highway at 2300 RPM (5th gear at about 60) and my gas mileage went down to 15 mpg. Does anyone have any solid proof of the gears actually making the truck faster?

 

I don't have any time slips for you, but from everything I've read that exactly what regearing to a lower gear like 4.10/4.56 would do. 2300 is what you would be cruising at w/ 4.56's and about 2100 w/ 4.10's. I just recently got 4.10's and my truck feels quite a bit quicker. Another thing to think about is the 4th gen reg. cabs w/ stock gearing from 3.21-3.92 vs. the 4th gen R/T w/ 4.10's and why those gears are in the R/T (quicker acceleration).