Reminds me of a boat with a hot bulb inboard engine that we once had - the exhaust manifold had rotted away. Irreplaceable, the engine was very old.

My university lab mechanic offered to make a new manifold - he used a steel plate and sections of a scaffolding pole. It looked a little like the above but worked perfectly.

We sold the boat and the new owners ripped out the engine and THREW IT AWAY AS SCRAP. Put in a small diesel. Philistine.