How far in the hole 318 pistons

Well, sorta. While it is true that compression dropped, it's also true that horse power ratings changed from gross to net. So that makes it appear that engines lost a ton of power from 72 onward, when in fact, they did not. That'a always a part of the equation people sometimes forget. With all else aqual, a 10:1 engine for example, will make only about 6% more power than an 8:1 engine. Compression alone isn't the end all be all a lot of people think it is.
Very true Rusty. The open chamber heads did have more tendency to detonation. Other factors in the emissions systems of the day caused drivability issues. The eengineers were having fits trying to figure out how to lower all the pollutants and be able to have reasonable drivability. The VW diesel emissions scandal is just another phase of the same thing. People that had their VW diesels reprogrammed to be emissions compliant all cocomplain power and fuel economy went down the outhouse hole. I used to wonder when you would end up following one of those cars, how they possibly met emissions. As a licensed automotive and heavy duty mechanic my nose said they did not. Nose was right.