I'd have to agree that the numbers don't tell the whole story. I've ran 351C 2v's and the 4v's. If you look the 2v's should kick butt. The 4v's are good for at least 50 HP. The 2v's run out of air at 5000 and the 4v's at about 6500. That's not to say the engine won't turn higher but that's where the power starts to drop off.
Comparing Cleveland heads to a SBC is like comparing apples to tires! A canted valve head should flow well. There's no way a C head will touch a 10 degree GM. As far as the #'s on the flow page went... guess I did a good job with a sanding roll on my big block Blue Thunders... 361/[email protected] You wanna talk about a head that sucks? try a 73 & later 460. I've seen stock 327 heads do better.