I suppose it depends on which head we start from but for the early round ports Im sure there is
some cleaning up and slight deshrouding that could benefit flow.
It seems that the pic with the black has too much material removed unless the inlet valve is made larger as the shrouding is necessary to create the swirl on the sparkplug side of the chamber.
Maybe a tad of deshrouding woul benefit the higher end it just depends on what its tuned for.
I would lean towards as much swirl as possible with boost.

I dont think if tubing is worthwhile compared to a well matched port manifold.
Its easier to work on the ports the traditional way while other engines it could
work where there is enough meat to tap a thread into the ports to screw in a threaded
pipe of the right dimensions.
Im more inclined to think about using a unitary rocker cover top of similar grade alloy
plate then you could lift the port beyond sealing surface.
eg.

Attach file:

---

  works roundie.jpg (112.06 KB)