Clutch End: OD :20.45mm or 0.808" and inside the splines is 17.25mm or 5.07".
I also have a AMC clutch and it is a good fit. Can you confirm that my mainshaft is the Plunger one ?
Do you have the part number for it ?
Please let me know if I can be more help. I'm in sussex where are you located ?
Regards.