Um, OK, this one wasn't mine, but it is the highest mileage powerstroke I have ever personally seen in person.
We had a rollback come in with 355,000 miles on it, needed a new motor because the guy ran it low on coolant and drove it like that for like 3 weeks. The block cracked and let coolant into 2 cylinders, he then checked the coolant level, and then had to keep refilling it over the next 5 weeks because it kept pumping the coolant out. Other than that, the motor looked excellent inside, most of the cylinders still had cross-hatching in them. We put a new motor in it.