Alternator light is need to 'excite" the alternator. No LEDs for that one. It can be hidden if you like. You just need it.
Some dashes that might help you....
My old Manx:
A yellow buggy that I did kinda old school. Blinkers, high beam & alternator light built into the stock VW speedo. No tach. Just wipers & headlights & speedo.
A Bradley GT kit car I did. I eventually used stainless steel trim screw washers around the LEDs to make them look more finished. I also had to run a regular bulb under the dash in series with the LED to make it work right:
A Porsche Speedster dash that used 914 gauges...they work perfectly. All indicators are in the gauges:
