...class 121 and 122 driveshafts worm drives and spare motors, i just motorised a dummy for around £20!!!!
You need two farish 12 tooth gears and a larger diameter 20 tooth gear as well as three splines for each bogey....
Or if you have a powered unit as well you can swap one geared bogey with a dummy bogey, runs fine with only one powered bogey, on test pulled four farish coaches too with only one drive bogey.
That is all :)
Very useful if you are considering the class 128 conversion!