diesel engines cost alot of money in matienance. Money that can be used for gas.
If you can find a good condition 7.3 in your budget id hop all over it. Dont get a 6.0 unless you are okay with spending 5k and up on making it dependable,
I'm super happy with my v10. A close friend managed to find a low mile, well kept 7.3 (2wd) turtle top with correct, low rear end gearing. I have serious engine envy over that thing. They are however not easy to find these days.
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'99 EB ex ENG KSWB news van, low rent 4x4 conversion (mostly fixed by now), home built interior.