I can only speak to the way my car was upon my purchase in '76 (and it appeared original, although one can never know for sure if a repaint was done), but I believe it to be original in regards to your questions:
1) the underside of the hood 'overhang' at the cowl was painted body color, as it is 'exterior' paint and the stripes didn't overspray (much) if any in that area.
2) the underside of the hood over the engine was blacked out; I *suspect* it a was a 'glossy' semi-gloss (like GM reconditioning paint), but I can not say for sure what they painted it with at the factory.
GaryW