Have you done a tuft test on the car yet ? That would show the problem areas on the car.
The 1981 Camaro had a Cd of around .45 - .48 ( It's been a while, so don't quote me on that. )
However, Hot Rod magazine took a 1981 Camaro and got it down to a verified
point two zero one Cd .
The car looks nearly stock. It even has the stock door handles and window trim. Even the fit of the body panels is a mess on that car, but they got a verified Cd lower than almost any car driving today.
Here is the article :
Car Aerodynamics - Hot Rod Network
Note there is a link to the pics at the bottom of the page .
If that doesn't work for you, this fellow posted the entire article here :
Wind Camp Hot Rod Magazine March 2007 by John Haag | Photobucket
Good luck !