It's all about peak cylinder pressures, and the engines resistance to knock (gets back to squish characteristics, and combustion chamber/head design)
I'm sure the Falc' with it's shitty 2-valve heads wouldn't have had a great volumetric efficiency (didn't make much power for a 5.8L motor), whereas a late model Ferrari or Porsche motor with their 11 or 12-point-something to 1 comp ratios would have huge peak cylinder pressures at high revs, due to the volume density of air the heads flow.