I'm definitely no expert, but something of a mild enthusiast.
The reason I own diesel pickups is because I worked as an EMT in college.

ALL of our ambulances were Ford 7.3s. They were SO beat on, and we had the world's laziest / chittiest mechanic on staff.
I seriously could not tell you what sort of a maintenance schedule any of the rigs were on but it seemed like never. $0.02 We destroyed bodies in crashes (ambulance bodies, hopefully not patient bodies), we tweaked transmissions, I personally had a driveshaft u-joint go on me which was exciting, but I never saw a blown motor. And because I worked for the cheapest ambulance company in all of the ghetto, we'd have 3, 4, 500k on these things. (edit: with a ton of city miles / extra idling) They'd always die in crashes before being "used up."

It was back then that I decided when I got older and had some money, I'd own a diesel truck. I always wanted a 7.3 - but have owned only a couple of cummins since.
Last for-what-it-is-worth thought - people rag on the 7.3 as "slow" compared to the competitors / newer stuff. These ambulances were WAY heavier than my empty pickup and i don't know if it was gearing or what, but I sure don't know where that "slow" thing came from. I'd definitely say "comparable" - if not quite as fast. You're not missing out there, again, IMHO. If I could find a really clean one, a 7.3 Expedition would be my dream truck.