The one time I had to do this by the numbers, I was tracking down A4 silver for a '66 Dart GT. The only place I could find undisturbed original paint was at the front of the underside of the transmission tunnel. I went into a PPG store and had them mix up a quart of A4 for the '66. It matched my undisturbed paint perfectly. I was really surprised because the paint used 7 or 8 different pigments.
The suggestion is, find undisturbed paint and compare your swatches. The outside finish of the car may be nice, but it has been exposed to 34 years of sun, smog, waxes, and other stuff. Good luck.
