Contain all the components that need to be installed on the pinion shaft for the specified year group. Kits for 1939-53 and 1954-77 can be used in 1972 and earlier engines to speed up the oil pump by 25% for more potential oil volume, since S&S oil pump drive gears are of the 1973 and later 6-tooth design.; Color coded to match the OEM color chart for pinion gears Biggest for 1939-53 S&S Big Twin Style Pinion Shaft Gear Kits: Black 913-761 Average for 1939-53 S&S Big Twin Style Pinion Shaft Gear Kits: Blue 913-762, Green 913-763 Smallest for 1954-77 S&S Big Twin Style Pinion Shaft Gear Kits: White 163-111, Brown 913-764, Yellow 913-765