The diesel cycle converts chemical energy to mechanical with less fuel. It has to run cooler this is physics. Petrol engines use 20-30% more fuel per combustion event than diesel of equal output, so btu per unit reasoning is a wash! In this case the energy per unit is irrelevant, one uses more fuel to make up for having less energy density.
I'm not spinning it any way. The 8.1l WILL overheat with an lb7 radiator. I've seen it first hand. The gas guys would love to use our intercooler because it works with there trucks with no mods, other than requiring the smaller diesel radiator. The gasser will over heat idling and most def under full power.
In the end, I do agree he needs a larger cooler simply for the safety factor (marine use). No argument there. Not here to argue just pointing out something interesting.
Wolf