Hi John,
If you have an original belt driven N5c then you will need the 610-140 mainshaft which has the stepdown for the lower bearing block.
If you have the N5c torque tube version then you will need the 610-410 mainshaft?
The clutch is the same on the original N5 and both the N5C Belt/TT versions, the part number for the clutch is: 200-405.
Hope this helps, if I can be of any further help just give me a shout.
Cheers,
Ross