As far as i can remember, all the Volvo duo prop drives have a gearbox built in, so the need for a seperate gearbox is not required.
Volvo do a kit (well not exactly a kit, as it is only available as individule parts
) to fit in place of the bell housing and then this will take a jack shaft, just like the original fitment setup.
The kit is a bit on th expensive side, you may need an arm and both legs as payment, but i have looked at the diagrams and it ain't that bad, or you could utilise something like a python drive.
