JohnZ, do you know the assembly procedure for motors with Ali intake? Was the intake fitted by the engine plant, or was the whole valley area covered off and the intake and dizzy fitted later on the engine dress line?
Silver overspray is typically found on Flint engines with aluminum intake manifolds, as there was a silver touch-up type process where silver was sprayed on the exposed cylinder head area between the intake manifold and the valve cover so that area wouldn't rust before the car was sold; during the initial orange painting, the aluminum intake manifold and aluminum valve covers were masked with a vacuum-formed plastic shield, so little or no orange paint got on that area, which would rust quickly without additional painting. All intake manifolds and distributors were installed at the engine plants. We see a lot of this silver overspray on Corvette engines, as most of them had aluminum intakes and valve covers.