The goal I use when wiring a classic Mopar is to keep any high amperage current drawing devices from passing through the bulkhead connector. I follow a modified Mad Electric method of accomplishing this. I also run a fused properly routed cable from my alternator output terminal to my 12V+ starter relay lug, and I bolt both Amp gauge wires to on side of the amp gauge.
I often install a volt gauge so I can verify charging when the car is running. Your stock amp gauge is ok to use if you can't stand not having your gauge work, but don't run more than your fatory amp load through it. The secondary cable from the alternator to your 12V+ starter lug will keep the high amp 12V+ charging current load out of your bulkhead connector.
Anything that uses more than 10 amps gets properly fused and has relays installed on the circuit. I power the relays through a 12V+ distribution lug located in the engine compartment, and that is often the starter relay lug. Of course, the typically 4 gauge cable from the starter relay to the battery continues the current flow from the alternator to the battery.
Also, I use Marine Grade components for any fusing, relay or wiring applications, high quality electrical tape and heat shrink tubing. I solder all my connections, but properly done crimp connectors work very well too.
If you properly wire the vehicle the only load passing thru the ammeter is what is needed to charge the battery. Nothing else. So it really doesn't matter how much capacity you alternator has or how much load you've put on the system. I just finished converting my 51 Plymouth to 12v and rewiring the vehicle. Still running the stock, original ammeter. Because the only load passing thru my ammeter is the charge for the battery, nothing else. As per the factory.
