i emailed said company about the items, they say that 'the products codes RD134, RD166, RD167 and RD136, can be coupled to the
original gearbox, without any problem As they are for racing use, the final drives aren't with ground teeth, so
they result noisier if compared to the original final drive ratio.
If you are interested in our products you can contact also Andy Gamble of
Playmini Company (andy@playmini.co.uk) who sells our products for UK.'
May be ideal for the be3/6 to make it a better track box, i know ratios will remain the same as stock, but the lower final drive will make acceleration even better and all 6 gears more useable.