i have a c6 with a 3.10 gear in a 1960 bird. the speedometer reads slow with the original 1960 gear. Anyone care to guess how many teeth i need? It appears to read 55 at 65 +/- a taste. The c6 was bought for a 1966 428 cu. Are there any 1966 3.10 gear ratio with the same size tires as the 1960.