I had both the genoa and ballooner sheaves replaced when I bought my SM this past July before I sailed it up to the Chesapeake. If I were you, I would change them both while you are up there doing it. The boat was in Le Marin Marina in Martinique when I bought her so I just had Amel Martinique order the sheaves for me. I checked the copy of my invoice and unfortunately all it said was "réas de tete de mat" or "masthead sheaves" so I do not have the part number or size to give you. I can tell you that they cost 29.10 Euro each. I would contact Maud in La Rochelle or Jean Collin in Martinique. I might still have the old ones on the boat. I will have a look this weekend when I am there and will report back if I do.
SM #440 Cara
Deale, MD USA