for reliable power and killer fuel mileage get an older 12 valve cummins. I have an 06 cummins and get about 15mpg. my old 12v gets around 20. not the most powerful truck on the road but the mpg is killer. i would also look at getting a manual tranny. my 12v had about 400k miles on it and when i took it out to put into my f350 i decided to rebuild it. tore it down and crosshatching was perfect and bearings looked awesome. hth.. just my .02...