Natl assoc of WHAT cars? Here's another banana, and another profile comparison of factory to race banana

Notice the differences in the 2 race cars, that Petty's was customized to race against all other "STOCK" road runners yet is obviously a ringer, the wheel wells are better, the c pillar looks smaller, looks like about an inch chop, and the rear tires look set back an couple inches, the truck looks more horizontal too.