Several years ago I reworked a set of std port Indy SR heads that went on a 493 with a Ede 6bbl manifold.
My recollection is it was a 10 second street/strip combo.
After about a year or so the owner wanted to try and step it up a bit, so he bolted on an untouched std port Mod Man 6bbl manifold.
Ran the same speed/ET.

That would have provided the option to open up both the heads and manifold to MW size.
I don’t know if that ever happened or not.