BEEN THERE, DONE THAT
I recently replaced all running rigging on my "new" 1983 O'Day 23 that had been on land for 8 years, out in the weather, and uncovered. I just took a foot of the old spliced end with hardware to the rigger and asked for the current version of that line, etc. If no rigger close to you, West Marine has a rigging shop on each coast, and the east coast shop did a good job on a couple of halyards for me. I added a couple of feet to the halyards I had made, but in the future would add more. I now plan to run the halyards back to the cockpit so I may need more length. Good luck