Great trucks
As for fords diesels: 83-87 were 6.9 IDI's, 88-95 were 7.3 IDI's, 94.5-97 were 7.3 Powerstrokes and 99-03 were 7.3 Powerstrokes in the Superduty platform.
It sounds like you're looking at the 94-97's so I'll leave the Superduty's out of this. I would have ZERO problem buying a high mileage 7.3 in the 97 and older chassis if everything checked out okay. I know many people with well over 250k on these trucks (one friend has a 96 with 780k last I saw it
) and still going as strong as ever. The auto trans is finicky but it can be upgraded to be very stout if you have some money to dump into it... The ZF5 (five speed manual) is great, but the dual mass flywheels can be a headache. Most have been converted to single mass by now, but you never know.
Some of my recommendations are: change the oil every 3-4k miles and use a quality filter. Not only is the engine dependent on clean oil, but so is the injection system on all 7.3 Powerstrokes. Keep a trickle charger on the batteries if its going to sit for long periods of time. On manual trans trucks check the firewall where the clutch master cylinder is. It is not uncommon for the firewall to crack here and make the clutch petal weak. There are aftermarket fixes for this, but they are time consuming to instal. Keep an eye out for an F350 for the solid front Dana 60 axle. The TTB D50 is not bad especially for a toy hauler, but there are a lot of moving parts and they can cost a lot to rebuild if they've been neglected. Glow plug health is the difference between someone who loves or hates their PSD... Replacing them isn't a hard job just be sure to use Motorcraft plugs and nothing else. As for intercoolers they could always benefit from one I don't consider them to be a deal breaker. If you chip it and add bigger injectors/turbo then it really becomes necessary, but in stock form (or +75ish HP) I wouldn't loose sleep over it). I've heard of issues with the steering gearbox shafts stripping out, but I've only seen it happen once so I don't know how big of an issue it really is.... On a brighter note Ford sold thousands of these trucks over the years so replacement parts used or new are everywhere
I would start a thread on power stroke nation, oil burners or power stroke. org and ask for recommendations there. The LAST thing you want to do is buy a PSD because it was cheap or a fixer upper. Take your time, spend extra if you have to and get one that isn't neglected, hotrodded, pulled way too much weight for way to long or owned by a wannabe street racer and you'll be good to go. Service history is icing on the cake but sadly few people ever keep track of it :-\
Despite popular rumors/myths (they suck, they're gutless, they're unreliable, they don't start in the cold etc...) I would not rule out a clean turbo IDI. I LOVE mine for many reasons and its one of the best diesel trucks I've ever owned. Anyway I hope this helps. I was far from a Ford fan until I bought one... They aren't perfect, but neither is anything else lol.
Andrew