Do you mean the clutch gear that replaces the main shaft output gear? Whatever, John Craddock
www.johncraddockltd.co.uk has most overdrive parts. You'll also need a lock washer. You need a 'special' tool to remove the mainshaft lock not, but you can't get it anymore. A punch and large hammer is usually effective at undoing it. You'll also need a new gasket to fit between overdrive housing and gearbox. You may already know this, so apologies if I'm teaching you to suck eggs. Do you have a copy of the fitting instructions?
