Mmmm...

Chuck,

do you have the Skymaster 60 plans? The header dimensions might be inferred from there.

Hatori tended to give a serial number to the headers for each engine and specific MK model name. However, some of those headers, although serialized differently, had the same shape. For example, the Aurora 60 and Beetle 60 probably used the exact same "fuse side bottom" header. In the case of the Skymaster (was that you who picked up the built one on auction?), it looks to be a fairly regular "fuse top" header since the exhaust pipe runs "a la Prettner Magic". Wouldn't a fuse top header with no side angle put the pipe right were you need it? Perhaps you could use a Mac's header made for an OS 61 RF (i.e. one of your Hanno's... )

Just some thoughts, David.