Is that kind of why engine lift brackets (for example) on an alum intake were left as natural finish? -Because they were masked at the time of painting?
What I mean is... they would have never separately received a coat of Chevy Orange on their own -just like an alternator bracket?
The plastic mask for the aluminum intake manifold mostly covered the lift brackets (which weren't used by the engine plant); for a while after they were introduced, the assembly plants were told to remove them and return them to the engine plants (cost savings), so orange brackets from engines with painted iron intakes were occasionally seen on engines with aluminum intakes.
My Production Engineering Group at the Chevrolet Pilot Line developed the corporate engine lifting brackets for 1968; photo below shows the number of engine dress line hooks on the left side required for multi-car line plants in 1967, with only two hooks on the right side required in those plants for 1968.