Here’s some early concept art of characters, drawn by Dave “Big” Deal in 2000, when work on Cars started. 
98% of the characters all have makeshift mouths. 
Sally: bigdealart.com/images/SampleFiles/Sally1.jpg
Interestingly, she’s a 993 rather than a 996 
She was also, at one point, going to be a Mustang. However, they made her a Porsche since the grill looked more “lady like”.
Lizzie: bigdealart.com/images/SampleFiles/Lizzie.jpg
She was originally named Henry F. Ord, she’s a Centerdoor Sedan rather than a Doctor’s Coupé 
Sarge/Fillmore: bigdealart.com/images/SampleFiles/Sarge.jpg
Both were originally going to be antagonists and Fillmore was originally going to be named Waldmire 
Luigi: bigdealart.com/images/SampleFiles/LUIGI.jpg
Mater: bigdealart.com/images/SampleFiles/MATER.jpg
Here is a rendered frame: en.wikipedia.org/wiki/File:Carsanimation.png
According to bigdealart.com/, Cars was originally intended for Spring 2005, then delayed to November 2005, then to June 2006. 
Dave’s latest work includes a major movie project for PIXAR, working with John Lasseter. Can’t say much more than that at this time. John just recently announced the movie to be released in spring of 2005. 
Lastly, as evident by a 2001 concept sketch, they were originally going to make Doc a Packard Clipper, as Mr. Windshield, who was scrapped from the storyline around 2003. 
McQueen’s number was also going to be 57, but it was changed to 95 around 2004/05, when production finished. 
