Mrs. Racer and I own a fleet repair facility in North Dakota, and I would say that the information in the article is supported by what I see here. Most units in our shop are Ford F250-F550, and they just seem to keep going. As for personal experience...Our 2000 Ford Excursion with the 6.8L V10 gas motor will turn 250,000 miles before the next oil change and is still running strong!
I've read about the Cummins turbodiesel engine swaps into Excursions. IIRC, there's an Allison automatic transmission from an F-550 that's a direct bolt-in for that engine and chassis combo. That would be one sweet custom rig and you'd get tired of it long before it was worn out.