matching paint is a PITA for sure. Fade and deterioration make it all the more difficult. You are right to try to find a area that is not sun bleached to match to.
Some PPG jobbers and/or shops that spray PPG have a color scanner camera (forget what its called) that may get you out of the "Doctor Pepper" range and closer to your actual color.
Many times the actual toners for out dated paint codes are no longer available. Metallics change, materials change, what was once single stage lacquer is now only available in base coat/ clear coat and water base paint.
Try to find one of the old color chip books for your year car to give you a actual paint chip , I see them on eBay or at car shows a lot.
Good luck, Rick