Edgemontvillage was referring to the engine orange on the head surface between the valve cover and intake manifold... ie. the upper part of the machined surface for intake gasket... which normally would not get painted on such an engine (with aluminum manifold and aluminum valve covers)..
I may be off base on this, and please correct me if I am. When engines with aluminum manifolds and valve covers were built, a shield was used to keep as much paint off of them as possible. That area of the head would have been painted, but maybe not as much as the rest and burned off leaving the impression that it had never been painted. On assembly line cars, orange over-spray could be seen on the manifold/valve covers verifying that point. Some restorers do not want to see assembly line features like that and prefer to paint the head complete and then install the manifold, eliminating the over-spray from it. Personally, I like the assembly line defects.
I have never seen any assembly pics like that. My 1100 mile 70 Z had no evidence of that at all. It has orange paint on the plug wire stands that were done with a brush.