M_Boats: Halyards and mast head sheaves on M17

The wire section on my jib halyard is not long enough to reach to the deck at the stem fitting. When the jib is hauled down the top 2 hanks are still up on the forestay. The rope to wire splice is stopped at the masthead. I can get a new longer wire spliced on, or I was thinking about converting to all rope. However in looking at the masthead casting, there is not enough room for wider sheaves to handle rope. The casting only has a 3/4" slot where the sheaves are mounted. Has anyone done this conversion to rope? If so did you have to change the mast head to another casting? Where does Bob get the masts and fittings from? Dwyer or other? Thanks Bill Wickett M17