1 - the boom to the top of the mast
2 - top of the mast to the base
3 - base to the clutch
4 - clutch to the winch
Add these up and that will be your halyard length
I would recommend a 6mm vectran based doublebraid such as V-100 or equivilent.
While you are at it, take a look at the clutch cam and consider replacing it at the same time.
pm me if you have any Q's