From what I've read , it's not the flow rate that's the problem with E-heads. It's said that the valves, springs & machine work can be much improved by having a knowledgeable Pontiac head guy machine & assemble bare heads, using better valves & springs.
https://butlerperformance.com/i-2445...tegory:1234814
Butler seems to indicate that they only sell heads they assemble, with porting included. I assume they would do a set without porting. But, I suppose it's possible that there is not enuff profit in the assembly alone. Don't know.
https://butlerperformance.com/i-2445...tegory:1394343
But, there are probably several members here who will assemble a set for you, without porting.