@Markerrag -- don't forget about fuel injection. When you combine the accuracy and precision of fuel injection with an overhead cam design, you suddenly find you are able to pull around 300 horsepower out of a six-cylinder engine through computer timing, high compression ratios and other such tricks.
Fuel economy can be improved, too, leading to vehicles with somewhat small engines that can produce as much as or more power than a muscle car from the 1960s while still being affordable to operate. More power without the "gass guzzler" problem. That's a winner.