Re: 2008 F450 thermostat and cavitation issues.
Do you really want to fix this issue? Look at all the work you get out of it.
This is not surprising at all. Higher rpms will lead to more cavitation. All pumps are susceptible to cavitation. Its simply a drop in pressure lower than the boiling point of the fluid its pumping. The faster it pumps, the lower the pressure on one side of it. So a lower geared truck will have more of a problem. That's thing one.
Thing two is fleet and severe duty vehicles go through parts faster, for whatever reason. Some of the parts make no sense, but have a separate change interval anyway based on "severe duty." Spark plugs are an example. Why do spark plugs wear out faster in severe duty applications? No idea, but they do. Injectors are another, but those make a little more sense.
Ground straps won't help because you're not dealing with an electrolysis issue, you're dealing with cavitation. The only thing you can do is flush the coolant more often, or put some additives in every so often. Either will work, but just changing the coolant twice as often is a better idea in my opinion. A different pump and or intake design would solve the issue, but that's not possible.
Ps...Im pretty frickin awesome!