I owned an '04 F250, with the 6 diesel. In the first 20,000 miles, it was at the shop 22? times. One of the first trips in was to pull the engine for oil leaks. They never did stop the leaks.
New turbo after several trips complaining about bad pulling power and missing. The troubles just kept coming until I had a "meltdown" at the dealer. They kept the truck for a week and when it was returned to us, it was a total different truck.
As far as a good truck, it was very good (body, trim, comforts), but the engine was from he*&%.
We had to purchase a new truck in 2010, and Ford had just come out with a new engine--I had been a test bed for them already, so moved on to another brand.
I never did any mods to the engine and even kept the stock tires and wheels.