Sealed beam conversion looked like a after thought so I went with the original reflectors and glass lenses in my 37 Chevy p/u but with 12 volt bulbs,well they need to be a little more brighter so is there a conversion out there for a brighter bulb maybe halogen that will work with my original parts.
Check out Headwinds.com for a conversion kit that uses an adapter for modern lights. Street rod section, headlight adapter kits - there's one for your 37.
You know, I've been accused of not being the brightest bulb in the chandelier... Oh that's not what we were talking about... see what I mean?
Do you get full battery voltage on the lamp (still connected, don't take it out to measure)? If you lose voltage through the wiring you lose light. You lose a lot of light. (Upside its that you gain lamp life, so it's a compromize.)
Coming back from a show last night it seemed like a bulb went out but while I was payng to get in they stuck a big sticker in the middle of the light that caused it to seem dim but I still need brighter lights oncluding the tail lights and will be a winter project.
You can hook them up through a relay to get full voltage to them. I'm sure there's a thread on here somewhere about how to go about it.
I switched mine out years ago for a Cibie headlight. I would bet your problem has more to do with the reflector then than light bulb or voltage. Modern lights direct the light in well designed patterns, the originals are just like large flashlights.
I have original 27 T headlamps. Reflectors have been resilvered. I am using 12v LED bulbs for the main beam, halogen for the dip and LED for sidelights. Even though these bulbs are way more powerful the throw is still pathetic - mainly due to the design of lens and reflector. However, due to the more powerful bulbs I can be seen better - if not see better. I've fitted a modern spot and fog on the front cross member and this makes it livable.
And back them they could not travel as fast as they can now so they were just hood enough for the time,I do like the original look but not how they function. I was going to put sealed beams in it but the ring that took up the space between the bulb and the retainer ring made it look like crap to me. If I could find a smaller head light assembly that would bolt on and made for sealed beams I would do that.