Is load range E that rough
 

Im thinking of getting some Bridgestone Dueler Revo's. I have a 2001 F150 7700. I'd like to keep the stock tire size of LT245/75/16 (load range D), because i dont feel like losing any performance or messing with the speedo.

So, is Load range E going to be that rough of a ride, since they only have C, or E in that size. If it's going to be too rough, what other sizes should I consider, and what kind of performance and gas mileage loss am I looking at.

You could look at some 255/70R16s, they are only about half an inch taller than your stock tires (speedo would be about 1.4% off).