There were lots of very fast cast manifolds back then. That's what most of us had to work with, especially those limited to single 4 barrel. It definitely raised the curiosity factor.
Edelbrock made a SBC Intake Manifold that at that time
was a departure from the norm .
we Dragstrip tested it on Benoit's B/ED , it made more MPH, but with a little slower ET we could not solve or fix
so went back to original Manifold
Edelbrock's then new Intake had very short runner length, very tall Runners and Plenum Entry Areas
that Manifold is probably a very rare Intake ... a Collectors item ???
i think it was only offered for 1 year or so ?? or even less ??
Chad might possibly know of that Manifold i'm talking about ???
there was another sort of rare SBC Intake Manifold by Holley, it was better than the 300-25 , i think it was 300-40 or 300-45
it looked like the predecessor to GM Chevy Bowtie Manifold ... both were very similar to each other .
Chad... i'm pretty sure knows about that Holley Manifold too