We own a 1999 F350 7.3 with 320,000 miles on it. As others have said a bullet proof engine. Still pulls fully loaded cattle trailers, car haulers etc. We live in NW IL and that thing is as cold blooded as they come. And it "Likes" to be driven. If you are only planning on hauling short distances you are going to carb up the truck and ask for a world of issues.
We also have a 5.4L V8 gas engine in my 1998 Expedition. It has hauled hay racks, horse trailers (smaller trailers) and other things with no issues. It currently has 264,000 (=) miles on it and I am hoping for at least 400,000 before I break down and buy another vehicle.
Be very honest about how often you will haul, how many hills etc you will haul on. Bigger is not always better and you will pay for it in gas mileage and repair costs if you are not using the older diesel engines the way they were meant to be used. We also have a 2012 F250 diesel. That thing drives like a car, speeds up really really fast (for a large truck) is the smoothest ride ever and hauls our 3 horses as if they are not even there. And we can get 15-18 MPG when hauling on flat roads (fully loaded) This is our replacement truck for the 7.3 - which my son now drives.
Diesels are more expensive upkeep wise. olil changes are $100 - fuel filters need to be changed at least once a year ($100) diesel in my area tends to be more pricey than gas, you have to have additive for some diesels
Do the math and be honest about where and how you are going to haul. My Expedition hauled 2 horses in a steel stock trailer for many years - we may not have accelerated really quickly but we could go anywhere we wanted.