Factory ammeter

The 75 model doesn't have the same amp gauge with all the load routed through it. 75 model has a remote shunt mounted somewhere outside the firewall ( I forget exactly where ). Your amp gauge is connected to the printed circuit board like all the other gauges. That is less conductor than the typical volt gauge has. So all the amp gauge failure stuff you read on line does not apply to your car.
The later models have power distribution through multiple fusible links too. Earlier models have lights and everything else routed through 1 fusible link. So you already have a separate and more direct supply to your headlights. Relays would take the current load off the headlight switch but that defeats the purpose of the cycling circuit breaker protection inside that switch. Its usually the dimmer rheostat on them that fails first anyway.