13/40 and 22s is 7.16 ratio, Stock gearing and 62 MPH.
12/40 and 22s is 6.60 ratio, Motor will be very torquey but lose top end.
12/40 and 20s is 6.00 ratio, First gear will be useless, and you'll run though the gears way to fast.
13/40 and 20s is 6.51 ratio, Same as 12/40 and 22s.
13/39 and 20s...