I know up to 1938 the high beam indicator was an accessory that clamped to the bottom lip of the dash. I'm not sure when they put the high beam indicator in the speedometer housing. If you don't have a socket in your 39 it likely was under the dash as well. If you can even find one hold on to your wallet. If you're not concerned about being "correct" you can do whatever you wish. Hang a small light under the dash or drill a hole in the dash & put al light there. Tie it into your high beam circuit. Whatever trips your trigger.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.