MerCruiser 43-37964 43-55812 43-35930 Forward Reverse Pinion Gear Alpha1 1965-73 Controls 100 HP -- 1988 &

100 HP -- 1988 & Newer

SO IDEALLY I would count your teeth on your current gear before ordering

You need different ones if you are using oversize pistons

7L 350 & Others

Not sure what other applications  it is supposed to go in

MerCruiser 43-37964 43-55812 43-35930 Forward Reverse Pinion Gear Alpha1 1965-73 Controls 100 HP -- 1988 &Early Style MerCruiser Pre Alpha One Gearcase Lower Unit Gear Set Roughly 1965 to the early 1970's Part Number(s) Included 43 55812 43 35922 (Pinion Gear) (19 Teeth. If it has 20 teeth it is the 1973 1977 gear set) 43 37964 (Reverse Gear) 43 35930 43 35930A2 (Forward Gear) General Application Compatibility MerCruiser Sterndrive Alpha One Lower Unit Complete Gear set That was generally found in 1965 Early 1970's models (Pinion, Forward, Reverse)