OEM replacement reference 35039-85 and *35039-84; *35039-84A. *Note: 978503 is for 85-86 B.T. with belt. The 978503 replaces 35039-85... but will also replace 35039-84/35039-84A. These mainshafts are identical but the 35039-84/A uses a different clutch hub key. When installing the 978503 make sure you use the matching 901385 / 37523-85 clutch hub key.High end racing quality has been the Andrews standard for decades. Components you can trust. All are made of the highest quality steel; heat treated for strength and ground to precise dimensions.