Update: I spoke with Rick at Galley Maid. He has been their windlass-guy since the 70s and knows my windlass well. They do not rebuild windlasses from this era, as they started using a different style gear box in the mid 80s.
However, they offer 2 choices:
1. Brand new replacement windlass - $5700.
2. New gearbox and shaft - $1750.
Needless to say, I will be taking option number 2 and reusing my motor, relay box, wildcat and capstan.
They offered to refresh my motor with new brushes and update the mounting bracket for no charge if I ship it to them. The only bummer is the replacement carriage bolts are $50 each, $300 altogether. I don't blame Galley Maid. They do not make the bolts and I am sure there is not much demand for 15" chrome plated carriage bolts.
I plan to re-chrome my capstan locally. The rest of the windlass looks fine. Altogether, with shipping, I expect the total damage to be around $2500. I'll be assessing the core damage this weekend. Hopefully it is limited. I'll post periodic updates.