I've decided to defer addressing the issue until the boat is in the water.
This is the plan...
1. Raft up with my neighbor's boat.
2. Climb his mast.
3. Connect jib halyard on my boat over to his mast.
4. Winch my jib halyard to pull both masts together.
5. Drop new main halyard tracing line with bicycle chain at end down inside my mast.
6. Fish it out the bottom.
7. Pull new main halyard through.
With some research from another thread, I read that the halyards all run behind the spreader bar (open to correction on this). I will loosen up my forestay and hank on the backstay tensioner. This will give me max rake to encourage the tracing line to fall down the aft side of the spreader bar.
If anyone has any further guidance, I'm all ears
Surgery begins sometime next week!