If ya replace and modify a few things on the 6.0, the only problems the 6.0 will give you is injectors. But if you are a stickler for oil changes and typical maintenance it will be few and far between that it even gives you that. The 6.0's are good motors, run great when they are running good. Ditch the EGR cooler, update the oil cooler, add a coolant filter and a few little things here and there and it'll be almost bullet proof as long as you don't run a big tune on it (there just aren't enough head bolts, and even with studs it'll still lift the heads on big tunes with alot of boost). The 7.3 had it's share of problems too. CPS's, fuel drain leaks, under-valve cover wiring harnesses, wastegate actuators, lift-pumps, injectors, TPS, etc. Ya it saw less problems from the start compared to a 6.0 but in reality it still experienced ALOT of issues. As for the best diesel, a common-rail 5.9 or a 12-valve cummins are the best out of the box options, and a 98-03 24v Cummins with updated VP44 pump and FASS or AirDog system are still good, and you can still convert them to a P-Pump which will make them even better than the early 12v. I work on these trucks everyday, and ALOT of 6.0 fords, but when we get one in, we usually get the customer to upgrade all the crap stock parts and eliminate alot of the downfalls to it. Working on them for a living, I'd own one over a 7.3 any day of the week. The 6.4's are really nice and the 6.7's are good too as far as Ford's, but still, the Cummins rules the roost IMO.
