While my info indicates Scott Atwater made Firestones in the 1950s I think you will find yours as well.Stroke is 1 3/4" bore is 2 1/8"Point gap is .020.
May use a Tillotson or Walbro carb. Fuel mix 1/2 pt. per gallon.
I think you'll find more help in the other outboards section. Also The Antique outboard club at www.aomci.org Just don't ask what it's worth.