Speedometer Gear

I just checked the 65 FSM and they don't list a 15 tooth gear. They do list a 16 tooth gear (brown) for a 6.70-13 tire and a either a 17 (orange) or 19 tooth (red) for a 7.00-13 depending on which transmission you have. I don't think I have a 16 tooth gear but will take a look.