Nice! I just picked up mine this past summer with 343k miles and going strong! Okay I'm kind of surprised no one's responded yet, but then again I did just join yesterday so, yeah.
Maintenance wise from what I've heard, and from what I understand is good to do on the truck:
1) Change your oil at least every 5k miles, that's the Ford recommendation.
These 7.3's use oil to fire the injectors, and when it starts breaking down with age the lubricity goes down, and it can cause premature wear on lots of vital engine components. Its a good idea with any vehicle to change the oil, so kinda obvious there. Though I kid you not, as an incentive, the truck will run slightly better with fresh oil in it. Change your old oil and throttle response will be just a hair snappier, you think I'm kidding, try it out.
2) Keep clean fresh coolant in the truck, I prefer to use SCA precharged in mine. Keep an eye on SCA's those are supplemental coolant additives and basically help prevent cavitation basically small bubbles that form in the coolant on metal surfaces from a rapid change in pressure, from forming on metal surfaces in contact with the coolant, when the bubbles collapse the water creates a jet and over time hammers down through and erodes the metal. Don't keep an eye on SCA's and you could get a hole in a cylinder wall, or erode your water pump over time too. Go to NAPA and ask for diesel coolant SCA test strips and they should know what your're talking about. They come in what looks like a medicine bottle with 50 or so strips that you dip in the coolant. Though using a fleet precharged coolant should get you well on in the right direction.
3) Change your transmission fluid, especially with the E4od transmission. They arent' known for being the toughest in the world and Ford recommends you change the atf every 30k miles.
4) Change differential flud
That's the most basic items other than say inspecting batteries, wires, and glow plugs. Also on a truck of your vintage and mileage, look at your brakes. These trucks have really powerful brakes and should have no problem stopping on time. When I got my truck pretty much all the brakes were bad, and I even had a drum brake fall apart on me causing it to not work at all.
Otherwise: read the manual, it might seem overkill, but look at the owner's manual for more info. It may seem like overkill, but if you really care about the truck it's totally worth it!
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