[Marine-58]

If you want to see your engine rpm with different gears, you can go to google and look up

Engine rpm calculator. There are a lot of them out there. Enter your trans ratio, rear end gearing and tire diameter. I have a th400 which is a final drive ratio of 1:1, rear end of 3.55 and tires 31 inches. That calculates to about 2700 rpm at 70mph. Exactly what the tach says. This may help you decide on the ratio you want.