Top of cowl should be body color and if its a Z28 should have hood stripe color overspray on top of the body color. Front face of cowl should be black on all cars, and the break line is right at the fillet where the cowl face breaks over to the top panel, Firewall will have body color under the firewall blackout paint as the blackout is applied last. A hand held mask was usually used to protect the body color on top of the cowl, so the match line can vary a bit.