Our drillers in the office have just acquired a 2007 F450 Standard cab which will have a gross weight of around 15000 lbs once the drill rig is installed on it. The truck is a six speed. They are looking to nock down better mileage and make some good power at the same time. What do you guys recomend? Mileage is much much more important. The 6.0 Pstroke is not very familiar to me as I have a 7.3 and have spent most of my time looking at 12 v cummins motors (reading up, i'm no mechanic). Thanks for the help!