You should read about the powerstroke problems on a Ford Forum. Basically, all versions of the engines, 7.3, 6.0, and 6.4 (each year has it's own personality...PROBLEMS) all have unreliable components. i.e. sensors, egr, and poor design flaws. But, when the bad parts have been replaced they all make very good dependable truck engines.
That sounds bad.
Why the heck can't they just fix the design flaws?
The 04 up 6.0 is better than the 03.
The final years of the 7.3 had issues too.
The 6.4 has too much emissions crap.
There are several schemes that people follow when they improve these engines. All are documented on the forums and when complete you have a really good truck engine. If you found a deal on one and do all your own work, its not that bad.
I have a tuned '04 6.0, it has been dyno-jet to 700 lb/ft of torque at the rear wheels. 120,000 miles, 21 MPG hwy, 19 city, and the only flaw to show up so far is the IPC sensor, injector pressure control. $150 to fix myself, Or $500 at the stealership.
I clean the EGR every 50,000 miles and dump the tranny fluid pan and re-fill every 25,000 miles. Never flush, and never total changed all the fluid at one time, so as not to shock the system with fresh fluid. Change the tranny filter every 100,000 miles.
Most important... Don't let a Ford mechanic near it.
I know several people who have a 7.3 with over 650,000 miles and the only repair work other than oil and fluids is they changed the clutch every 300,000 miles.
Some people have 300,000 miles plus on the 6.0, they aren't old enough to have racked up more. It really isn't the engine that has problems lasting, it's the electronic crap that can't take the under the hood temperature. Most powerstroke forums have people who claim to have prematurely replaced turbos, and sensors, and injectors due to a stupid Ford stealership that couldn't diagnose the problem correctly, later after repeated problems thay found a $7 wiring harness adapter had failed due to the dry rot or heat next to the turbo manifolds. Ford having already charged them for the replacement part. You have to really try hard to trash a turbo in less than several hundred thousand miles, but the turbo pressure sensor can fail in under a thousand miles. Engines don't need all this electronic crap.
My advise, buy an early 80's chevy crew cab 4x4 with a built 454, it will get 10 MPG max, and it will cost $5000, put another couple grand into making it pretty, and run the **** out of it, then 5 years later drop a freightliner or detroit inline or cummins in it. It will be cheaper long run.
It seems that even with a new truck, you have to built it to make it the way you want.