H'm. So on a standard '75 wiring, the ammeter is a part of the battery feed to the main splice. So the wiring is heavy - 12 ga or larger.
On a '76 a remote shunted ammeter is used. The ammeter leads connect to each side of a shunt. They are only 18 or 20 gage. Hardly any current goes through them.
AFAIK '76 uses esentiually the same starting relay and circuits as earlier and no interlock (used in 74).
A1 is from the battery
S2 is from the ignition switch - hot when key is in start
S4 is the ground through neutral safety switch
S5 is to the solenoid terminal on the starter
Top Cowl - Don't know why its above the flange in 76 but it was.