I'm a diehard ford guy, but chevy's duramax is a very good motor. Great power and mpg. I have a 03 Ford Excursion with the 7.3 and it still gets 20mpg on the highway with 280,000 miles on it. I had a 05 with the 6.0 in it and it was an okay motor but not dependable at all. The 6.4 is not proven and ford has already ditched it to build the 6.7 in house now, which from what i've seen is an amazing motor! I'd love to have the new 6.7, but the problem is that it's new and no one knows how it will hold up. I'd say get something old enough to have the 7.3 or get a duramax if you want new. As for mods, i'm about to redo my X. I got rid of my 08 f150 because I was sick of the payments and would rather have a diesel again, but my X needs a few things that I just ordered. I bought a 4 inch lift, 35 Toyo M/T's, 18" XD Diesel wheels in chrome, powerslot cryo rotors, Hawk LTS pads, Banks CAI, Edge Evolution CTS programmer, and magnaflow exhaust. I'll get some pics when it's done.