400's are they any good?

Just a question here? Why does everyone say that a late 400 or 440 needs high compression to make power? From what I know starting in 70-71 383 block even some HP blocks had their pistons down in the hole pretty good. I understand quench makes more horsepower but, tell that to a guy who owns a 73-74 Super Duty Trans Am. What was the true compression on those? I think it somewhere around 7.9.1 or something like that? I think cylinder pressure is just as important as quench.
Ever drove a 69 383HP with a Mopar 284/484 cam and the rest of the setup was stock? My 360 feels stronger in comparsion than that combination.
Selecting the right cam and getting some head work done is important as well as the converter and the gears. If anybody sticks with the low compression slugs stick a cam on the small side that builds cylinder pressure and doesn't bleed too much of it off is what I was told.