No.... it won't fit.
There are two sheaves in that slender space sharing the same axle, the sheave is only .28 inches wide. You're better off replacing the wire to rope halyard with another one... 40x40 1/8" wire/ 3/8" rope. Or... if you want all rope, consider a "tapered" halyard....that was my solution and I'm extremely happy with it. Here's a link to a post I made a while back describing the whole thing. For more, search the archives for "tapered halyards" http://archives.sailboatowners.com/pviewarch.htm?fno=210&sku=2006224050127.69&id=416874&ptl=#2006233020811.56