The ratio charts can be your friend. They will provide you with the proper ratio to keep you engine at the proper rpm.
While we have had several discussions with regards to gear ratios, and I will bring back up a few key points.
Far too many folks are concerned about highway rpm's and they believe that the lower the rpm's the better. While this is fairly true for most cases, many fail to realize that vehicles have to still produce a given amount of torque to maintain foward motion. If the ratio is too high (numerically lower) like under the 3.0 range, and the taller tires of a truck is not compensated for, the truck will be foreced to work harder to maintain the same speed, and would be counter productive. Chances are, it will take more throttle to just slightly accelerate, and if too much throttle is required, the transmission will downshift, taking the engine rpms way higher than it would if the truck was equiped with a better gear.
As long as we are talking about acceleration, we should also discuss how often this vehicle has to start from a dead stop. This ratio wil make it diffficult to maintain speed, it will also make it more difficult to roll from a stop. All of this will take a toll on mileage averages. This is where a ratio that provides a mechanical advantage is far superior.
The weight, and the tire diameter of a full size truck makes me really have to suggest the right ratio for a given application, and a ratio that is suited for a lighter car, with shorter tires may not be the best for this truck.
Tire size is an important factor that has been left out here.