I think cam was definitely a big one. Split duration cams weren't really a thing back then (Apparently Ed still doesn't believe in them). And the lobes/ramp rates were wayyyy different than what we run now. Some of the cams that we don't think of twice running on the street would be considered "radical" or "race" cams back then.
The other big one is exhaust scavenging. Tuned port exhaust. And what not. The effect of exhaust on the ability to fill (or overfill) the cylinder is huge. Exhaust does way more work to draw air/fuel into a cylinder than the piston does. This is why Ed mentions the 100 percent VE. Because they hadn't quite figured out then that you could actually achieve a higher VE without some form of boost. That by increasing exhaust flow and using tuned exhaust to increase/pull the intake charge across the combustion chamber and therefore make the engine more efficient. They knew you could cram more air in with a supercharger. But didn't know you could cram more air in simply by tuning the exhaust properly. A lot of what they worked on was the intake side. Of course we now know the huge effect scavenging has. How it clears out all the burnt hydrocarbons. And ensures the cylinder is filled with a good fresh mix of air/fuel. And in the right ratios you can get 100 percent combustion. Which obviously is ideal. They obviously knew scavenging existed. But I don't think they knew it's importance on N/A engines then.
