Yes right from the get go along with W8's but to be reasonably sure I think that a P7 head will outperform both of those 2 at max effort levels.....pretty sure....not 100% sure
Jerry Arnold( you may not have heard of him, but national record holder in comp eliminator, extremely respected head porter, yada, yada…Rest in peace)….had a P7 head on his bench a few years back…busted 400 cfm… he was amazed by how nice those heads are.
I have heard several high end guys say it has more potential than any other small block head.
I suspect the fact the R5 was such a short decked creature, and nothing else existed to bolt it to( until now with a Ritter block) that the likely hood of people throwing together a big inch P7 combo kinda passed the market by.
Don’t know of any such efforts undertaken, maybe Kent Ritter would know