Alternator Gauge Reading High With 300 Watt Stereo System Installed---1969 Electrical System

In my 67 fish, I have a 200 watt head unit in the dash and a 200 watt Bazooka base cannon in the trunk. The head unit runs on OEM wiring and signals a relay that powers the Bazooka amp from alternate source/wiring. No charging system issues but... I had already upgraded to later model 65 amp isolated field charging system long before adding the jukebox.