There is nothing about a NASCAR racer that is like a “stock” car. The frames are tubular welded, motors and transmissions are nothing like what you buy off a dealer lot. They just paint the front to look similar to a real car. How they make the headlights look real is true art.
NASCAR doesn’t have any pollution standards to be concerned about. And the motor generally is running at a high and higher RPM’s so not a issue how it idles or takes off from a stoplight smoothly. I wonder if there is any kind of computer engine management systems in these racers at all? The ignition systems are probably pretty much old technology too.