Exactly, if dodge was allowed to run there hemi head, and ford was allowed to run there cleveland heads, then shouldn't chevy be allowed to run there BBC with the splayed valves, or even the LS based heads with the really tall and narrow intake port, and raised exhaust port? I don't necessarily see the advantages in hp, I mean, lets face it, the good old days of the rat motors stomping the small blocks is over, and the aftermarket as well as race team R&D have brought along THE best flowing heads ever created, where I could see an advantage is say the HEMI, they are more efficient, require less fuel, therefore, tire only pit stops. Also, there is darn near nothing shared between the production engines to a nascar engine! They aren't even hardly bored and stroked the same! Bigger isn't allways better, remember the 302 vs 350 sbc? Were talking about engines that turn 8-9000 rpm for 500 miles!
Were talking about 6 bolt main caps and main journals the size of big block cadillacs! IMO, the engine R&D is soooooo good that there is no way an engine could make the difference in a race, that is if it holds together. Just the fact that those motors hold together, an old pushrod based motor at 9000 rpm is amazing!