I don't trust old school magazine quarter mile numbers. Look at what those guys were working with for tires. And those production cars were so saddled with all kinds of BS from the factory that made them slower and heavier than they would have been in the hands of a decent tuner.
Just look at what basic cam heads and intake mods do to a factory car, even from that era. You can make a lot more power pretty easy. Go watch the Richard Holdener video where he mods a Mopar 360 out of a 70s era dodge van. He makes damn good power with very modest upgrades.