Split the gearbox this morning. Not a pretty sight. A good layer of black sludge in the bottom. Gears and drive shafts covered in a layer of rust. Main bearings rough. I did manage to free the selectors and get three gears.
So I reckon it's a total rebuild, with my metric conversion like the C-121. Not going to happen methinks.
A visit to a friend today has produce some interesting parts, that with another engine I have, will make a fun special.