stock for the 12 inch tires is 145/12 or 145-80/12
Hunt around the junkyards for a 17 tooth speedometer gear off a 96 up metro to fix the error and not have to deal with calculating the mileage all the time. The 12 inch tires had a 18 tooth gear so a quick and dirty way I think might work to correct the speedo/odometer error is (actual speed = measured speed * 18 / 17)
