We have a couple of older 6.0s at work. They are driven in a very commercial application. When they are started, they are driven all day long. No short drives to the grocery store, no commuting empty to work. One had a trailer for 99% of its life, only coming off when the truck went in for service. Only little things needed fixing. Biggest one I remember was a rear main seal.
Those who bought a 6.0 as a daily driver and sometimes pulled a trailer on a weekend, The ones in the employee parking lot. Those were not happy. They always had issues. Typically dumped really fast after warranty. If not there was about $6k dumped into the refresh. Everything from ARP head bolts (which I understand are approved by Ford) to EGR delete, coolant filters, and a good collection of parts from Bullerproofdiesel.com. With all the good parts in, and typically a bit of an aftermarket tune, they were happy owners.
As for buying a 6.0, I would look for one that is stock and in good running condition. The price should be pretty low since they don't have a good reputation. Then put all the good parts on yourself. And all of them, leave one off and you might as well not do any of them. Then you will own it forever because it will still never be worth what you invested in it. Hope you like it.
As for the V10, watch the years because some were will known for blowing out spark plugs. And I think some also had the broken 2-piece spark plug issue as well. Although I do recall that they were rated as the best choice for a motorhome. The initial costs were less, maintenance was less expensive as well. Yes, they drank fuel. But that excess fuel costs never caught up with the price of the diesel.
As for the ambulance reference... That goes back to the mid 80s. Ford was having issues with gas powered ambulances catching fire. The carburated 460 gas engine. Nobody could figure out why. The easy fix, only sell the ambulance package in diesel. And that lasted until the contract with IH died. The 6.0 was the last engine that would fit the 70's Econoline chassis. The 6.4 didn't fit, thus you could still get the 6.0 when the trucks had the 6.4 engine. Ford and IH in those last years was not a happy relationship, forget the lawers there were judges involved in enforcing contracts that neither wanted any part in. Thus Ford built there own 6.7 engine without IH. At that point the Econline was on the deathbed and no attempt was made to stuff the 6.7 into the chassis. But Ford still wanted to sell ambulance chassis. So they pulled there diesel only policy and started selling the last few years of the Econoline with a gas engine only. After 30 odd years of no gasoline ambulances, now that is all you can get.
