There has been a lot of dialog on many of the online forums about halogen conversions to the pre '40 vehicles.. The general consistence has been that they don't work. From my own experience with my '39, I converted to 12v halogen, they did work very well.
The problem with the halogens is that the original '36-39 bulbs are what is referred to as being "pre-focused" ... the head light lens prisms are made to work with that type of bulb. The halogen conversion puts out a lot of light which is not focused on the road because the focus point is all wrong.
I converted my '39 back to stock reflectors and Painless' 12v Bright bulbs.. These bulbs fit the standard '36-39 socket. The light is more concentrated onto the road.
I know several people that tried mounting conventional sealed beams behind their stock Ford lens... This does not work very well because the stock lens prisms dis-fuse the light. There are clear lens available to use over the sealed beam conversions that work very well, however, you loose the stock look.
Many people have their reflectors chrome plated in lieu of the original silver plate and/or "glass" plating. Generally speaking, the chrome plate does not work as well as the original type of silver plating and/or the modern "glass" plating.