Ford headlight bulbs were 2330 style from 1935 to 1939 so if an LED bulb fits in a 35 it will fit in every year through 1939. 1940 was the first year for a one piece headlight bulb with the glass lens as part of the bulb, the headlight had the typical three flat electrical terminals at the rear. There seem to be many people on this web site that are using LED headlight bulbs. Some do not like the result and some do. This is most likely due to the LED manufacturer used and the resultant light emitted and how it is focused.