You can buy modern seal beams with the top section blocked off to create a signal light " built-in ". You may be able to duplicate this setup by adding a bright metal " partition " to separate from the headlight so it wouldn't get lost in the glow ?
You can convert from parking to parking / signal using a 2 post socket & bulb.


1940 Chevy KC 1/2-Ton
In the Stovebolt Gallery