Speedo gear 1970 A904 selection
I did the math for your tire diameter, and it came out at about 27.0 inches (it could really be rounded to 27.1 if that makes a difference). I used a chart on drivinithome.com, and it only shows diameters of 26.8 and 27.4. The value 26.8 technically is closer to 27.0 than 27.4... if you were to go by that you'd want a 32 tooth and a 35 tooth.
