1965 Barracuda 273 engine 904 Torque flight.ENGINE SWAP....

Dan the man said

So, a flange for a header has to go between the cylinder head and the exhaust manifold on the driver's side? I don't want to say at this time why I'm asking these questions. And I'm not trying to start anything

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That's the easiest and surest way to deal with the interference (which is only an issue with mid '70s and later heads). Some claim to have been able to use double exhaust gaskets, or grind the interfering part of the port flange away, or a combination of the two. More often than not, grinding the head in that area just hits the water jacket and junks the head.
Note that this is with the early A manifolds, which many times are the only option in these cars depending how it is equipped- ie power steering, etc.