GM Body Styles
Here is a quick graph to help identify the more popular GM body styles from about 1964-1979. Wouldn't want to refer to your 69 Nova as an "F" body now would you?
Wouldn't want to forget the G-Body either, GM used this designation for a mid-size RWD platform from 1969-1972, and again from 1982-1988.
Another occasional stumbling block is the various generations of each body style. GM was relatively good at changing things every couple of years, so knowing the correct generation of your classic comes in handy. Below is a chart listing the generations up to around 1977. (Yes, we know many body styles were made after that, we just do not carry parts for them.)