cleaning up the slant six head

I think that you're wrong, that most of us do recognize that, have processed it, and are now asking "what can we do that is reasonable?"

The difference is turbulent flow vs. laminar flow. Sure, you aren't going to easily and cheaply turn a low flowing head into a dyno killing 9.90 monster but you can make a difference in the quality of the flow that you do have. Reducing the turbulence, reducing the boundary layer will promote better flow without resorting to serious and time consuming port development work.

The tone that I get is one of throwing one's hands up in the air, wandering around saying "there's nothing that can be done, there's nothing that can be done..... " when that really isn't true. something CAN be done, it just isn't going to make it a fire-breathing monster. It will help with efficiency and it will help in making a little more power. It is worth the effort to gasket-match the ports.