Foy, I was looking at that generation of Fords with the 7.3L diesel, and even high mileage examples were commanding very high prices... like $20K - or more - Canuck money. If it isn't rusting out, I'd have it thoroughly checked over and keep using it forever.
Having not had the old 7.3 liter diesel out on the highway for more than a few miles at a time since August 2020's 6,700 mile Montana trip, I decided to run her to Virginia Beach and back Friday-Saturday on an emergency plumbing repair job on our 70 year old beach cottage (seeing any patterns here?). Conditions were optimal in each direction of the 420 mile round trip--A/C not needed, flat as a pancake topography, no headwinds, off-Interstate routing most of the way leading to 62-68 mph cruising speed range. Odometer-corrected pencil and paper MPG was 16.8 and that is within 0.5 MPG of what the onboard system says. The interval included around 25 miles of stop and go in town plus a half-dozen small towns' stop and go each way, otherwise for pure highway use I'd have seen 18-18.5 MPG or so I believe. And she purred like a (rather loud) kitten the whole time.
In the next couple of weeks I'm going to change the ATF and its inline filter, motor oil and filter, and send samples to Blackstone Labs per normal. If I get good numbers back like I have several times previously over the last 17 years, the decision will be made.
With that, I'll install a new cooling system overflow tank, upper and lower hoses, fresh coolant and needed anti-cavitation additive, thermostat, serpentine belt, change the rear diff fluid, whatever else seems wise at the time, throw a new fuel filter and a CPS sensor in the truck toolbox, and by late Spring have her ready to roll.
She won't quite reach 300,000 miles by the time we return, but she won't be far off. There's always Big Bend country late next year to reach that milestone............
Foy