Over the years I have had a Ford 7.3 F250, MB 300SD, Excursion 7.3 and a Dodge 2500 Cummin's. I myself would steer clear and did of many 6.0 Fords. The turbos and head bolts, warped heads - "fix" only with non- Ford parts where you can is my understanding. From what I took away it's the top end of the motor which is the problem and the turbo - think Banks as a replacement... I know two people who took it on and they each put ~8K to 10K in as labor costs were high. They sold the trucks not that long after so it makes me wonder.
I know someone with a trucking firm 200 plus over the road units. He drives a gasser even with diesel fuel tanks and mechanics right outside his door. Now I understand why he went that way. I lost an injector due to a small dirt particle and got a dealer quote of $8K to do the work - wanted to change all the injectors $875 each. I'm pretty knowledgeable in some areas, so I did it myself and it cost $800 in parts (did nozzles and plungers) and one or two special tools. Took a bit to get it all done and I have many shop tools to help. I would not want to be on the road needing diesel mechanic assistance and would not do that job without access to a shop of tools.
Humbly, I think the new gas engines taken care of will offer +400K miles. The gas is cheaper, generally mileage is not much worse -2 mpg, parts are by far more available, almost everyone can work on the gas engine, parts are less expensive, it's quieter, fuel is more available sometimes. As explained by others the diesel will last long time (possible 700K miles) with maintenance of oil, better fuel filters and fuel conditioner (every tank fillup). The diesel will pull all day long with lot's of power as stated above. If it were a Cummins or Duramax I would be more inclined to say go for it. As for the 6.0 my understanding is it almost tanked Ford because they were replacing ambulance bodies onto new chassis because the failure rate was so high. I personally know a guy who had two new 6.0's they were both in the shop more than he had them at home - engine problems. This is why Ford built their own engine (6.7) and tested the dickens out of it before releasing.
All that written many have made the 6.0 work and many are still going - just be ready to put some bucks in when it fails. If it fails on the road it's gonna cost you way way more than a top notch, fully rebuilt, wiz bang new gas engine. Unless, there is a need to tow I don't think the costs will ever balance with that diesel as the fuel cost difference is a wash in mpg. Go gasser unless you want to roll the dice!
