… for my Gen Halyard which was wire spliced to rope, mine were probably a bit wider. Many years ago I switched to all rope. I kept the same sheaves for a year or two, they seemed to work okay. Soon after I removed the Sheave, sent it to Ed at Zephyrwerks in Port Townsend, he made me a new Sheave, and the difference is amazing … the halyard zips up & down effortlessly. That's what I would suggest, have your friend contact Ed. I now have all his Sheaves on my mast.
Cheers, John