Pretty much full body F1 or Indy Car. So many rules, intake manifold specified. Crip sakes, if ya need to pass gas you pretty much have to ask NASCAR permission.
I liked racing when it was more run what ya brung. The Mopar crews had the winged wonders, Ford brought out the Talledega. Ford introduced the SOHC, but everyone else cried foul so that go banned. I believe the Ford and Chevy guys tried getting the Hemi banned also.
The early Can Am Championship was great with all the inovation that went on.
The F1 arrogant snots got rules piled hi as a flag pole. Now whoever starts on the pole is pretty much guarranteed to kiss the beauty queen. The F1 snots think the answer to bringing fans back is more power. Arrogant pricks don't get it. Put the excitement back in with passing, drifting around corners. Simplest way to bring costs and speeds down is to use a spec tire with a DOT wear rating of say 200. Investing $millions only goes so far when you are traction limited. These tires wear with fine dust instead of marbles. This opens up passing in corners. Fans would come back.