British and Indian shafts were both imperial, changing to metric who knows when. The old imperial shaft size was 16.35mm and the new shaft is 17mm.
According to Henry Price at Pricepart mc's the bearing should be a 6303 with a 17mm diameter hole.
If you have an imperial gearbox and wish to fit an extended metric shaft you will also have to fit a new metric bearing housing or modify the original. Just don't be tempted to hit it with a hammer!
