The wiring diagram included in post #17 appears to be one of Nacho’s, from the B-body/Charger forums. I see where it could be easy to do but consider it a band-aid fix to leave the original run in place. I agree, a quick disconnect there is unnecessary and only introduces another potential point of failure if the disconnect is under current rated, as most are. On my builds, I only run 8ga straight from the fusible link to the ammeter and replace the original 12ga run with an 8ga direct run from the alternator to the ammeter, via firewall gromet. Leaving in place, at the ammeter, the original dash harness black ammeter lead, to feed the factory loads.
The diagram also indicates a parallel by-pass of the original alternator to, bulkhead to ammeter. This reduces the current through the bulkhead connector only, will not alter the ammeter accuracy. The straight alternator to battery/starter relay by-pass some suggests does affect the ammeter accuracy, may or may not be by one half. In Parallel circuits, each leg of the circuit would have to have the exact same voltage drop for it to be one half, not likely to achieve this with different sized wiring and crusty bulkhead connectors left on one leg. The ammeter would be rendered effectively useless. Yes, the E-body ammeters is not scaled in amps, however the movement used in this ammeter is the same movement used on other Chrysler platforms of the time, some are scaled to 40amps one way or the other. Some Police applications used the same movement with an internal shunt and are scaled to 80amps each way.
Most electrical professionals will advise not using parallel runs in these types of circuits, difficult to predict current loads on each run and are difficult to troubleshoot later.
The pictured vise-grip clamped to the ammeter leads screw & nut, appearing to touch the steering column support bolt head startled me a bit, assuming the battery was/is not connected.