Thanks mrfixit, I had not thought about that aspect of the situation, but..........I can state that in tests, we have run the engine in our shop at idle RPM only, and it still blows the fuse.
When I get this truck back to running order on Monday (7/23) I will definitely check the system voltage level....at idle and higher RPM.
Not sure if idle RPM would be sufficient to raise the voltage to a harmful level with a defective voltage regulator, but it will for sure be looked at now.
Pondering that possibility I would presume voltage reaching 16VDC or higher would be the smoking gun in this shooting.
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