I'm sure this will ruffle everyone's feathers lol. If you're that set on reliability get a 6.9/7.3 mechanical or even better a B series Cummins with the dowel pin addressed. There's one thing about people that will never change, their passion. Shen someone feels that their choices and preferences are the best option they won't listen to reason or rationale. I've read as many threads about mystery problems with the 7.3 just like the 6.0 and just about every other computer controlled engine. Everything will have problems over time, whether minor and major, and will have to be dealt with.
That being said, try to find something that has been maintained well and not abused. Perform necessary maintenance, delete if there are emissions and you can, and then enjoy. Just remember, no matter what you have, there will likely be issues at some point and you will have to address them and continue on your way.