This is the vid of Jeff Gordon talking about NASCAR's implementation in GT5 and his role in it. Also he is really excited use the nascar cars on non nascar tracks (which is a good point of the whole nascar experience). He also discusses the right way to draft for Nascar cars.
https://www.gtplanet.net/jeff-gordon-featured-in-gran-turismo-5s-nascar-events/
https://www.gtplanet.net/jeff-gordon-featured-in-gran-turismo-5s-nascar-events/