HALFWAY, that is compelling evidence of original engine color paint on that hose bracket.
Do you know the Time Built code for the Lemans?
Gotta wonder if the Engine Assembly Plant started including the hose bracket as part of the engine assemblies as a running change resulting in them getting painted?
I'm doubting that if only because they would have to be removed for an A/C build.
Maybe they chopped a few cents off the cost by eliminating the plating and painting them instead, also as a running change?
Yours looks to have the same deep groove as Rich has, the one that is painted on his engine. So maybe his is correct after all.
The variations that are popping up here make it seem impossible to pin down what was correct when and where. Possibly different vendors for different Plants. Possibly the vendor was given the option of painting them Pontiac Engine Blue or plating them.
Wonder what original evidence the '64 big car guys would have? They were assembled at many more Plants.
Here is one on ebay right now, claims to be original with original "natural" finish.
http://www.ebay.com/itm/Original-GM-...item25d3dc8a39
Only one pic so can't tell if it has a deep, shallow, or no groove.
Posting the pic here to preserve the evidence.