[blucar]

My concern about adding secondary lights to your '39, or any other vintage vehicle is that generally the added lights don't look right.
The tail lights on a '39 are all ready dual filament lights, stop and tail, very easy to hook these lights up to turn signals. Of course one concern can be brightness.
To improve the brightness of the light clean the inside of the light housing, paint it white, white is more reflective than silver. Check all of the wiring to the tail lights for a good clean secure ground and power source.
The front lights present a problem. There are several small LED type lights that can be mounted on the front bumper, on the lower edge of the fender, etc.
I have a '39 conv, the other brand, that has very similar tear drop tail lights as the Ford does. I cleaned the light up and painted it white inside. The 12v tail lights are very bright on tail and stop.
For added safety I had some custom LED lights made that would fit within the bumper over-rides. I used red for the rear and amber for the front. The aux lights are hooked up to turn, stop and 4-way hazard.
I have received many positive comments over the years for my lights.
I am putting a similar light system on my '36 Ford coupe using a column mounted aftermarket turn switch.