I owned an '83 F250 (6.9L) for years. Awesome truck with nearly zero problems.
A couple of years ago I went through the same search you are now doing. I opted for an '01 F350 7.3L with 65K miles. These low mileage, later model 7.3s bring a price premium, but this is a far better truck than a 6.0L. Like any vehicle, they have a couple points to watch -- mainly the Cam Position Sensor (check for recall replacement on this), and there is some vulnerability with the injector wiring loom failing. I had this happen and an International Diesel mechanic shop repaired in an hour for less than $200.
Other than that it has been trouble free and a good performer. On the Highway I get 19 MPG. Towing my Airstream, I get about 13 MPG. I have put about 100K on the truck - no smoke, and no additional problems.