Not sure how you would propose testing that. If you run the heads OOTB then that is one test but if you allow someone to port the heads then you end up with a completely different answer.

Even though this is the race forum I'd wager that most of the guys on here run heads out of the box. If you include the TF240 heads in the OOTB category then I think they are a good contender. I suppose Indy might have a good standard port head too although most of their stuff is MW size with a necked down face to make it standard port.

The other issue with your question is that it all depends on the size of the engine, the cam and the compression ratio. I'm pretty sure a guy could build two different engines to get two different results.