So, for what you are pursuing, if we look at this older iron head in the picture:
Then the newer iron 2V head getting prepped for the port divider:
It is obvious that both heads from the factory have a compromised center port as they came from the factory. However, for what you are after, maybe not so much of a compromise.
Now take a look at these extractors:
and these shorties:
We can see, though there are individual pipes for each cylinder, the center siamesed port allows both #3 and #4 cylinders to hit those same 2 center extractor pipes. This includes both the exhaust gasses and the sound wave pulses.
From a sound perspective, this situation is almost the same as a set of extractors with the 2 center pipes crossed and the 2 center ports in the head being separated, either by the divider in an old head or a newer head like the alloy shown at in the top pic. The difference being, crossing the center pipes with a head where the #3 and #4 are separated will be better for performance. The sound might meet your rumble requirements a little better too.
Does that make sense?
Back later with more.