No, I'm pretty sure you can use the 20V clutch and flywheel in a T-50 box (I have just done this myself). It's only the ZE clutch that is too big. The input shafts are all the same, and the 20V clutch is the same as the 100kW clutch. It should just bolt up oh... except for the plate between the block and bell housing, you need a RWD one.