Historically, it takes a High Riser, or an SK Medium Riser, to go head to head with a rectangle port BBC.....at least in the world I came from. Stock and Super Stock are a pretty good yardstick for comparing the factory iron. The A, B, C and D Super Stockers, and A and B Stockers show this. You won't see a Cobra Jet until SS/E, and in Stock they run much lighter than the 427/425 and 396/375 Chevrolets. Still, with the 10% stroke in the rules, the CJ combo would get a longer arm than the Chevs, which would help from 3500 to 6300. Without a big roller, or RPM and using the closed chamber head, the BBCs may not be invincible. For sure, they will be ultra competitive. I am going to look through my stash and see if I have anything interesting in the corner for a 428 that fits the rules.