I found relays and 6v halogen bulbs made for lights as bright as any modern car. Relays save your switches and sealed beam bulbs produce proper beams. I could not find any 6v led headlight kits for 1940 Fords.
There are halogen housings that you could fit a led bulb into, but I do not believe you would get a good beam and would probably blind other drivers.
The stock 1940 bucket accepts a 7" "industry standard" sealbeam, "6014" 12 volt, "6006" 6 volt. There are a wide variety of direct replacement led bulbs and conversion kits as these lights were used well into the 1970's.
They work but as I get older I don't drive at night but end of month have to do a wedding in the car and it will run into the night.So that is why I would like to get brighter headlights.