If you want your ammeter to be something other than a non-functioning hole-filler in the dash, there needs to be some way of monitoring the current flow in and out of the battery as the vehicle is running. If a heavy-gauge charging wire goes straight from the back of the alternator to the battery, the ammeter will be bypassed, and it won't function. I'd suggest finding an original-equipment wiring diagram for a 65 truck with gauges instead of idiot lights to use as a reference as to how the ammeter functions with the original remote-regulated alternator and figuring out how to adapt the circuit to accommodate the newer internal-regulated system.
Jerry
