As mentioned in the Early Designs thread, clay models were an important part of the initial designs.
Here are two more clay models. Neither one made it into actual production.
Picture 1 is a from 1965, a Camaro Nomad.
Picture 2 is from July 14, 1966 - on the left is a Camaro 2 Seater. Clay models could only stay outside a short time in the Detroit summer heat. Notice the regular Camaro, possibly a pilot car, in the right side of the image.
Photos and information - credit to GM.