keydet86, you can just use regular Pontiac Metallic Blue engine paint on an aluminum manifold. I've been spraying intakes for 30+ years and never saw one peel the paint. Aluminum is a natural heat sink, so the paint won't flake off like it would on steel.
I painted a set of Edelbrock aluminum heads 15 years ago, and to this day the paint has never peeled, burned, or discolored, even over the center exhaust ports. They still look like new after all these years, which I've always been happy with!
As to why the factory did not paint RAIV intakes, that was purely a marketing thing. They wanted everyone to notice their new hi-perf aluminum RAIV intake, which was their first factory aluminum intake since the old 1963 SD421 days. Other manufacturers, like Chevrolet and Chrysler, began using aluminum intakes, and they left them natural aluminum too as it added to the "racer" image of their engines. Afterall, what good is having a hi-perf aluminum intake when no one knows it's there?
When Pontiac, like all the Detroit manufacturers, began to focus on emissions and economy in 1971, Pontiac painted their 1971-1972 455 H.O. intakes blue to lessen the "racer" aspect of their cars.
