Isn't it interesting that there were more rules for the body than for the running gear? Reading the magazines of the late '60s, there was a continuing attempt to maintain slot cars as scale model race cars – there's even an interesting letter to the editor polling the major drivers of the era about whether to stay with 7/8" rear tires or return to 1". It seems the NCC rules were a last gasp at semi-scale rules, as well as a last gasp to control costs so the average Joe or Jane could be competitive, at least at their home track.
What is nice to see today is that from Retro to hardbody to oval track to drag, and some flexi classes, a majority of 1/24 slot cars racing today look more like 1:1 race cars than the doorstops we had for a long time (and, of course, the 1/32 cars are miniature works of automotive art).
And the interesting thing is that, with the exception of flexi racing (birthed by Parma), a lot of this came from the bottom up, created by racers.
Life, at least at the track, is good!