65amp wiring/trouble shooting

Mattox the big wires through the separate grommet are known as "fleet taxi police" wiring and are used with factory optional 65A alternator. OP that wiring IS IN FACT a partial "bypass" from the factory and bypasses most of the current around the bulkhead connector. You are lucky, few of these girls have that setup.

That setup is not well documented in the 74 manual as the wiring diagrams are rather AFU.