Take Grand Am and ALMS as an example, mix in real American auto industry technology and innovation.
I'd build the chassis with a central spec carbon fiber "survival cell" like Grand Am, fuel cell in front of the rear axle.
Have the front and rear "clips" built with tube frame extensions so Billy-JimBob has got's something to weld on, sheetmetal body, so's them good old boys has got something to hammer on.
Spec undertray that creates the majority of downforce.
Independent rear suspension, aluminum components. sequential shift 4/5/6 speed spec. trans (depending on the track). 17" wheels, at least 2" wider, much bigger brakes, carbon/carbon.
Weight: they'd have to get the cars down to something respectable, 2750lbs. that's 650lbs lighter than the current "trucks".
Engine: with light weight and serious downforce, these cars would be on par with Grand Am, I would use a similar equivalency formula for the engines, Fuel injected, nothing over 4.5 liters, all aluminum, 4 valves, overhead cams or 2v's and pushrods, some of the smaller engines should rev to 11k!
Cornering speeds on ovals can be controlled by hp. output of the engines. E85 or 100% ethanol for fuel, possibly a Diesel equivalency too.
I want our "premiere" sedan series to actually represent the current and future U.S. car industry.
When was the last time a car was sold in the U.S. that used a carburettor??

Gona build myself a castle, High up in the clouds.
There'll be skies outside my window,
Lose these streets and crowds.

Will find myself an ocean, Sail into the blue.
Live with golden swordfish, Forget the time of you.

Dance myself to nothing, Vanish from this place.
Gonna turn myself to shadow, So I can't see your face.

Dance the night away.

Coupe specs displacement chart U.S. 5cyl. engine codes and specs trans ratios vs. speed