I just jumped forward 2 years, it's a 68. He also posted the VIN. Dec / Jan car.
Denis,
I'm familiar with what you are saying, but what matters is what the window sticker said, which was Z28, not a code they happened to use in production.
4P also can indicate a L30/M20 car. Don't think people would call the first 16 Z28/L30 cars.
