[Run to Rund]

Back in the 1960s, the new cars dominated some classes, like C/S by 442s and GTOs, etc. Most people couldn't run such expensive cars and weren't competitive with older combinations in the upper classes. There was some room to build power beyond factory ratings with the new cars, but NHRA had seen the older stuff long enough to have a handle on their real HP vs. factory ratings.

The biggest issue today, imo, is that superchargers and turbochargers can add some power or a lot of power, depending on many other things. It is very hard to rate an engine that has so much variability. Then, when altitude comes in, the blown engines lose a lot less HP than normallly aspirated engines, so altitude factors are another big problem when trying to be "fair" to both normally aspirated and blown engines.

I have looked under the hoods of the new stuff and I sure wouldn't want to have to work on them, compared to the big engine ccompartments and simple plumbing of the 1960s, lol.