The bulkhead connector is a source of constant problems. Worst are the large BAT and ALT feed-thrus which often overheat and melt the plastic, causing things to touch which shouldn't. Best is to bypass that within the engine bay (search "MAD Bypass"). It disables the dash ammeter, but cars haven't had those since 1980's - use a cigarette lighter voltmeter. Only exception is 1963 & 1965 cars w/ buss-bar feed-thrus. The female terminals also often come loose and push in so you get erratic or no connection. You can bend the latches to correct. Cleaning is prudent, then fill w/ silicone grease.
Wiring is fairly simple to follow in these cars, just put your pencil on a wire and follow it thru the schematic, noting color and gage. The main theory to understand is that only current flows. Voltage is like a pressure in a fluid pipe. If two locations are on the same wire with no resistance or component in between, they will see the same voltage. The other thing to understand is power = current x (voltage drop) and that turns into heat.
