Ford diesels have their good and bad years.
The 86-87 6.9idi is a good one, but slow unless you add a turbo.
The late 80's early 90's 7.3idi is also good as long as you have prooven mantenance. Specifically the SCA level in the coolant. The cylinder is thin enough that cavitation can eat through it without care. A very ugly condition.
They went powerstroke(new block, high pressure oil pump(HPOP), computerized) in '94 and didn't get the bugs out 'til 97. So the '97 and 2001-2003 are also good. There were some changes in '98 and powdered metal rods in 2000 that concerned people. Powerstrokes are significantly more complicated and expensive to fix than the older models. But there's more power stock and more aftermarket support.
The 6.0 has been hit and miss. The '06 and '07 seem ok.

Don't forget to look into the Dodge/cummins. If you are looking for simplicity they were not computerized until 1998.

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I suggest we solve high gas prices with environmentalists... unfortunately they don't burn well.
1982 300CD, 220K miles: This vacuum system will be the death of me yet! (OBK #26)
1977 F150 400 C6 2wd, 10.2 sec 1/8 mile with 2.75 gears.
1965 Mustang. Mostly stock... LOL!
2001 Ram 2500, cummins, 5spd, 202k miles.(girlfriends)