You need to determine the length of halyard you need. If you don''t know what it is pull a messenger line through the mast attached to the bitter end of the halyard and remove and mesure it. Next you will need to decide if you want to use wire/rope or all rope. If you choose all rope which is prefered these days you will probably need to change the sheeve at the top of your mast. If you stay with wire /rope you just need to order the proper lenghts from a rigger or sail maker and use the messenger line to re-reeve it.