RPM at 70MPH

Hate to sound contrary, but what we have found with the heavier trucks is that the hemi likes 2100-2300 at cruise and gives the best fuel mileage in that range if running free, meaning not pulling extra weight. The lower rpms cause the engine to lug a little and needs more pedal to accelerate or just carrier itself at cruise. Of course this has a lot to do with the vehicle weight and aerodynamics which the trucks have working against them. With the weight being lighter and aerodynamics better the sweet spot will move down some. I would guess 2000-2200 would be the sweet spot at cruise. Anyway this is what I have found with my truck as I've modified it over the years. Unfortunately it is a poor example at the moment with several mods being done and tuning incomplete. Plus I'm now using a 46RH trans with a .69 over drive on 29" tires and a 4;10 gear. Assuming you are running short tires I would think the 3;73 or 3;91's would work great. good luck..