Sonny I think you could revive that 7.3L diesel if you had the right people work on it..a lot of the dealership techs just don't know the older stuff,its a rare tech that can UNDERSTAND what's going on and repair it,not just throw parts at a problem and hope to fix it..on your dollar..I know Ive said it before, try Powerstroke Specialty in Buford,GA..they will set you straight on it..they might even have a good 7.3L in stock that you could bolt in yourself..anyway all those older engines are getting VERY hard to find,even the 2000's are being junked..hard to understand where it all went..there were so many of them made..it is what it is,one way or the other it'l cost you money..GM is even working on a hybrid drop in replacement for older trucks hence my joke ealier,supposed to be a hybrid drop in electric powerplant, 250hp with standalone hardened electronics..GM demonstrated it in a '70s Blazer of all things..read this:

ECrate GM drop in replacement