I've seen several Six BBL Superbirds at shows who's owners claimed their car was original, but some had aluminum intakes. I though Chrysler switch to cast iron manifolds very early in the 70 production run which would suggest no Superbirds came with them from the factory.
My friends bird had an aluminum Edlebrock six pack manifold on it and the car was all original.
a discussion about these manifolds https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2728452/when-did-chrysler-switch-to-cast-iron-six-pack-manifolds.html (https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2728452/when-did-chrysler-switch-to-cast-iron-six-pack-manifolds.html)