Hi Jason I would probably have to rebuild your own gearbox but could convert it to overdrive at the same time. The mainshaft probably needs replacing anyway so an OD type wouldn't cost anymore. I could probably find a J type overdrive to rebuild and the conversion parts are available out of the UK. If you do the OD conversion we/you would also need a gearbox mount and plate, some bits for the inhibitor switch arrangement and the switch that goes on the steering column or an OD gearstick with the switch on the top. The column switch is correct for the Vitesse. You would also need to shorten the propshaft as the gearbox with OD is longer than the non OD box I used to run a Triumph service shop for many years and have done many gearbox rebuilds and overdrive conversions. I now work at Upper Classics a restoration workshop in Chch. Have a look at our website if you want to see the work we do regards Terry