The current Nationwide series has Mustang and Challenger bodies, while Chevy still uses the Impala. However, the Camaro body will be used in 2013:
http://www.insideline.com/chevrolet/...ar-debuts.html
Unfortunately, it appears Dodge is dropping out of all NASCAR series (trucks, Nationwide, and Sprint Cup) in 2013.
The closest thing to Mustangs, Camaros, and Challengers racing together is the Grand Am Continental Tire Sports Car Challenge (GS class):
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2011 Summit White Camaro 1SS/RS
-6.2 LS3, TR6060, 3.45, G80
2004 Black Silverado 1500 2WD Regular Cab, Short Bed
-5.3 LM7, 4L60E, 3.42, G80
2014 White Caprice PPV
-6.0 L77, 6L80E, 2.92, G80