The OEM sheaves were:
    2 1/2" OD
    1/2" wide
    3/8" ID, Oilite bushing
    V-Groove for wire/rope: 3/16" wire, 7/16 rope
    Rig-Rite Part Number K-198-10AB6
In 2013, I converted to all-rope halyards, and had new sheaves made by ZephyrWerks  
http://zephyrwerks.com/.  They were fast and reasonably priced.
The new sheaves are delrin, with oilite bronze bushings.  I had them grooved for 3/8" line,
and used VPC for the halyards.  Now, if I uncleat and release either halyard, the  sail falls
all the way to the deck without effort.