Gooseneck sheave assembly for reefing lines?

[memelet]

My boom currently has the reefing lines going to a winch on the boom. The placement of the winch is/was way forward, requiring me to move outside the mast pulpits to use the winch (just another WTF).

So I would like move the winch to the base of the mast under the gooseneck. The problem is that I need a sheave assembly with cams built that can be bolted or welded on the boom. I would prefer if it could be bolted on as I've (stupidly) already had the boom painted.

Does anybody know of any pre-built assemblies, as the cost to fabricate seems to a bit steep? The yard I'm working recommended that I look for a prebuilt if possible.

BTW, are there any pro/cons to placing the reefing winch at the mast base vs on the boom? (Assuming the boom winch is moved further towards the gooseneck, that is).

thanks!