our friends have a 04 6.0, they have had the typical problems with it and also a generator and high pressure oil pump.every fix seemed to cost from 3000 to 5000. They were lucky for the 1st 150,000 miles.No problems.
They don,t haul anything at all with it.
It's a Kingsranch and it's her daily driver. It now is pushing 300,000 miles.
They are still happy with it, in spit of the expensive repairs.
Her brother and nephew have had 6.0s in their loging bussiness and they ran them with chips but not until they bullet proofed them and then they had transmission failures.
If you could find a low mileage 7.3 you could switch to that.
I think if I were you I would take it to a really good independant diesel shop and run it by them and see what they would suggest It shouldn't be that big a mystery about the current problem.
Good luck