I can't speak for everyone else, but when it comes to certain safety-related issues that concern any old car I own and drive, there comes a time when function must outweigh form. A good example would be the vehicle's brakes. The last thing I want to do is plow into the back of some idiot whose brake lights aren't working ... or vice versa. Along with ensuring that I've got functioning and very visible rear lighting, I think it's not only important that others see me coming, but that I can see where I'm going as clearly and brightly as possible. To combat the negating of "form", most vehicle safety upgrades can be done very discretely, and that definitely includes converting '30s-40s headlights to halogen-without anyone being the wiser ... till you turn your lights on.
One of the main physical attractions next to its grille (or shall we say to each side) of many prewar makes, are the Art Deco bullet headlights. Unlike their modern descendents with sealed-beam bulbs, updating in the past typically meant sacrificing one of its unique charms-the bulbous, fluted lens. On top of that, re-silvering reflectors isn't cheap either, so even if you were able to incorporate a 12-volt type bulb, you may not really notice the difference in illumination with dull reflectors. There is one other option, however, which will provide the high-intensity glow of a halogen lamp.
Chevs of the 40's not only has a complete halogen conversion kit, but replacement Tilt Ray-style headlamp lenses, trim rings, seals-pretty much anything you could possibly need to modernize those old pre-sealed beam-era relics. And to further update the frontal lighting-both for your sake as well as others'-a Juliano's turn signal kit can easily be incorporated while upgrading your headlights.
To better facilitate the conversion, which wasn't designed specifically for the early Chevy headlamps in the first place, it's probably best to use the original reflectors as a means to mount the new ones. If you no longer have them or your lights were converted to sealed beam at one point (like these), try scrounging up a set of used ones (don't waste your money on a good set-they're not cheap). Fortunately, Bowtie Bits was able to unearth a usable pair of '39 reflectors-but you can also facilitate ones from other years/models. Even with this minor modification on top of the additional turn signal installation, the entire halogen upgrade shouldn't take more than a couple hours, tops.