The 6.0L is a fine engine...millions produced and still on the road testify to that as a fact. There were more recall issues and higher than expected warranty claims as a result of the emissions control devices/systems added and other short-term cost savings decisions (that cost more money in the long run). Ultimately you may let the "bad reputation" work in your favor to get a lower price so that is a positive from a certain perspective. Leaving the truck explicitly stock though is not advisable...understand that I am not speaking of performance modifications here so please don't get the impression I am about to recommend such:
1. Stock gauges on the 6.0L are inadequate in precision and accuracy - if present at all.
Engine oil temperature (EOT) and engine coolant temperature (ECT) are used to indirectly assess the oil cooler's ability to effectively manage oil temperature. The oil cooler is a stacked-plate, liquid-to-liquid heat exchanger. It is quite small and degraded capability of the oil cooler leads to many of the "problems" that are unfairly ascribed to the 6.0L. The stock ECT gauge does not provide ANY precision or accuracy; it has a needle that sweeps from "C" to "H" and is not linearly calibrated to provide any idea of temperature other than "it isn't hot yet" or "oops, your engine has overheated." There is NO stock gauge for EOT.
If towing ever interests you, the stock transmission fluid temperature (TFT) gauge operates the same as the stock ECT gauge; inaccurately and imprecisely.
There is no stock fuel pressure (FP) gauge. While the 6.0L has a wide operational band of FP, decreased FP is a fact of life for the FP regulator spring...materials degrade over time. The only way to know that FP has dropped without using failed injectors as a gauge is to add an aftermarket sensor and gauge...that's right, there isn't even a sensor for FP on the 6.0L.
Getting back to towing, exhaust gas temperature (EGT) is not measured by the 6.0L either so a pyrometer (sensor) and gauge are the only way to montitor this temperature. Monitoring EGT is good for turbo health to avoid overheating the turbine and to prevent coking of the turboshaft at shut-down...a seized turbo is costly to repair in time and funds.
Fortunately, the modifications to monitor these pressures and temperatures are minor. A digital OBDII gauge package (such as available from Edge or SCT, etc.) or computer interface (such as AutoEnginuity or Ford's WDS tool, etc.) with an FP sensor (screws right into the FP test port) and a pyrometer (drill and tap into the exhaust manifold or downpipe).
2. Exchange coolant to a no-silicate based extended life coolant rated EC-1 from the stock Ford Premium Gold. Use of Premium Gold won't hurt your truck by itself...but it is "advertised" as long life with a 100,000-mile change interval (or 50,000-mile if tap water is used to dillute to 50/50). Unfortunately, even out the bottle Premium Gold is below the industry accepted minimum concentration of nitrite. Failure to properly maintain coolant in a diesel engine is more significant than subjecting the engine to heat/cold. Diesel engines - as a compression ignition engine - create cavitation erosion. This erosion process literally eats an engine apart from the inside. Additionally, the mixed metal construction of the 6.0L requires sophisticated corrosion protection against iron oxidation, aluminum oxidation, and other alloy oxidation. The simple fact is that Premium Gold - without proper use of the Ford additive package - is inadequate to the task of 100,000-mile cooling system protection. Maintaining the proper concentration of nitrite is critical...that's why an EC-1 rated coolant is superior to stock. The EC-1 coolants have higher nitrite levels and use more sophisticated cavitation protection chemicals to prevent oxidation and corrosion too. Maintenance of these levels is still critical but you can expect longer than 50,000-miles between cooling system fluid exchanges. Ultimately you can run any coolant as long as you want...the result is that the low-silicate or nitrite depleted Premium Gold will not prevent oil cooler blockage typically resulting in EGR cooler rupture and inevitable introduction of steam to the combustion chamber where excessive pressure may induce headgasket failure or tented heads.
A coolant flush-and-exchange to EC-1 rated coolant is a simple if somewhat time-consuming job (about a day taking it easy). It is a task that genenates familiarity with the engine though. Perhaps this isn't even a modification although it is a detour from strictly stock construction.
Some things to absolutely keep stock: oil filter, primary and secondary fuel filter, transmission fluid filter. Fortunately, there are places other than the Ford dealer to get these although in the big scheme of things, filters are MUCH less expensive than engine or transmission replacements which are very possible when using non-OEM filters. Parker/Racor makes the oil and fuel filters for Motorcraft and International and NTZ makes the transmission filter for Motorcraft and International. Get the filters at the Ford or International dealer or order online from: Home - Diesel Filters,Additives,brake rotors, and brake pads for Chevy, Dodge and Ford Diesel Trucks
in the 6.0L section.
The 6.0L is a good engine with a few modifications that ought to have come from the factory in the first place...the modifications are very inexpensive, simple, and not very time-consuming.
Have fun looking!