MR01 is the 1993 - 2000 NX5 variant.
MR02 is the 2001 - NXA variant.
The major parts like crankcase and cylinders are different. The crankcases have different mounting points.
You can modify NXA cylinders to suit NX5 (MR01) crankcases but not the other way round.
I think the basic layout of the gearbox internals are the same.
The cranks seem to be the same for both models.