Elree are you out there?
Assuming it's like a 1970, the ammeter is a tiny voltmeter, that measures the voltage drop across a "resistor". This resistor is the length of wire between the junction block that hooks to the battery (+) and the horn relay (that is used as a main distribution block).
So one wire goes to the horn relay outer screw terminals, and the other one goes to the junction block behind the battery next to the radiator.
Is this the same on a 1968...I'm not sure.
Assuming it's like a 1970, the ammeter is a tiny voltmeter, that measures the voltage drop across a "resistor". This resistor is the length of wire between the junction block that hooks to the battery (+) and the horn relay (that is used as a main distribution block).
So one wire goes to the horn relay outer screw terminals, and the other one goes to the junction block behind the battery next to the radiator.
Is this the same on a 1968...I'm not sure.