As you will no doubt already be aware, none of the usual searches for parts for this engine come up with anything useful and it looks to me like your outboard option would be the best way to go. Re-engining with another inboard is likely to be more expensive and complicated.
Leith (rhymes with teeth) is the port of the City of Edinburgh in Scotland. A Leither is someone who comes from that area.
I must go down to the sea again, to the lonely sea and the sky - I left my shoes and socks there, I wonder if they're dry?