I second the recommendations for getting a 2003 or earlier 7.3 Super Duty. I have one with about 250,000 mile on it and just recently replaced the transmission - not because it wore out or failed but because I just felt I was pushing the envelope at that milage and did not want to get standed somewhere.
The truck is a fantastic towing vehicle, and even when not towing is not bad as a daily driver. That is the only vehicle we have to use when we are gone snowbirding for three or four months each year.
I feel it would be worth the search to find a 7.3.
Barney