Need to replace the halyard sheave in a 26' wooden spar, and can't find anything in my catalogs that come close to fitting. Anybody know where to look for a sheave scored for 3/8" rope; sheave to be 1/2" thick and 3 1/2" dia. ? Old axle was 1/2", but we could bush that hole to smaller diameter if new sheave had smaller home. A 3/8" axle would be plenty strong. Would not go below 1/4" though, as axle might have to hold the weight of a man going aloft in a bosn's chair.