im looking at using this pinion set and this c/b, but obviously with the other pilot shaft type nut. probably with a savage alloy 3 shoe clutch and flywheel from e bay as they are pretty cheap on there.
http://www.gmmodels.co.uk/acatalog/Ho_Bao_Spares.html
the pinion set part number is 18907 i believe, there is also a 12/16 set - 18908. i think those numbers are right... hopefully they will will work ok with my 43 and 39t spurs - ie, the front wheels might be on the ground once in a while...
let us know what u find out rolland, i wish i had more shops here i could wander round trying out stuff.