Your particular starter, #1107009 is a pre-war starter number used from the late 30s to very early 40s and then it was changed to a different number. The date code 8L15 tells me is probably was on a 39 model truck because of the very late date. This date code is just the build date of the starter and not the truck itself. The 8 is for 1938, the L is for November, they did not use the letter "I" on dates, it was skipped, and the number 15 was the day of the month.
That starter had very few differences all the way up until the end of its run in Late 53 for the first series 55s that were still 6 volt. It was completely interchangeable with any year model Chevy 6 cyl. truck from the late 30s until 50s. Your starter is still a 6 volt starter. The only way you could use an actual full fledged 12 volt starter from a 55 second production and up starter is to change the starter drive in the starter, as mentioned above by Cletis, different flywheels thus different drives on the starter. And yes, that is something that can be done.
Feel free to private message me for more info on the brushes, springs etc. Its all available and I can help you out.
Ken
