Vintage Racing Class Index??

I tried a google search, even tried nhra.com, but couldn't find the answer. Any drag guys out there that can list the basic classes used in the late 50s/early 60s, and what they mean? Like A/D, AA/D, B/ D, etc, etc. and what each class signifies and how do I figure out what label my car would go under? 70 dart 451 stroker (400 b engine) built trans, rest car is stock.