Thanks everyone; I like the engineering-style approach. I’m going to take measurements of the old fan. It turns out the 30A fuse has indeed blown as well. That fuse sits by itself in the front engine bay. The power cables leading to the fan are also scorched. Yes, it happened during a slow-speed section of a rally. We shut the Morgan off and waited for it to cool down. I lost the rally.
From your image above and having 12 inch (305mm) blades with assumption the fan sucks cool air through the rad it looks like this one drawing 12.4 amps would fit from the current Spal range. Please check these dimensions though and accept that the later design, having blade protection and mounting on the periphery, may require you to re-engineer mounts.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone