When looking at a used 6.0, there is one thing to make sure you check on, whether it has been tuned. If it shows ANY evidence of being tuned, walk away. Things to look for are gauges, aftermarket exhaust, aftermarket intake, anything. Many people throw a big tuner on these things and just trash the trucks and they will be nothing but problems. In order to tune these things and not blow head gaskets, you need to replace the head studs, which is typically an expensive procedure. Tuning with no studs equals big problems 9 times out of 10. Now, if the truck has been kept stock and towed, they can make great tow vehicles. As a rule of thumb, the later the year the better. After 2005, they really started to get them figured out and had worked out a lot of the bugs. Once you get it, first thing you want to do is add an external collant filter which will run you a few hundred and save your motor from problems related to contaminated coolant. Check out thedieselstop.com or some other sites that will outline what you really should do to make your truck bulletproof for years to go. When properly maintained and cared for, you can get 100s of thousands of miles out of these trucks.