No charge

Okay, I'm needing some advice. 1966 valiant /6 nephews car. Was having a charging and starting problem. Starting problem solved with a new ignition tumbler. Charging system still an elusive mystery. Had alternator tested, it was a newer unit anyway but it tested good. Replaced resistor, solenoid,regulator, battery (was bad), cables, connectors to alternator, still wont charge the battery. When we bypass everything and jump from alternator to battery it charges. Loom is old, but no obvious suspect wires. Did replace one that looked iffy. I know I'm overlooking the obvious im sure. Weather is getting cold and rain in the forecast so gotta get the nephew back on the road as he is walking to work right now.