I'm not trying to bump this thread, or resurrect it from the dead (page 2) but I have another alternative screw base bulb.
I already mentioned the Terralux tle-1s as being an upgrade led screw base bulb for vintage headlights.
There is also a bulb made by Tektite that has a screw base. The model LS407 is a 6v screw base bulb that can be used on vintage lights. There are other models that will handle 2,3 and 4 c-d cell lamps.
There is a difference between the 2 in their design.
Has anyone made a comparison between the two bulbs?