Anything past "natural" on the exhaust manifolds just doesn't look right to me, sorry. Even the "cast blast" paint it too dark, by observation. Any paint on the exhaust manifold would cook off, anyway, over time.
One time, a Pontiac magazine article mentioned that painting the exhaust crossover area with high-heat paint BEFORE the final engine color was applied would make the normal paint last longer before it discolored from heat. Of course, you could paint the intake "dull aluminum" to mimic an aftermarket aluminum intake. Can probably find some high-heat aluminum color header paint for the undercoat paint layer?
As noted, the exhaust heat was there long prior to electric chokes. General intake manifold temp is needed for good cooler weather warmup and drivability.
When I rebuilt the engine on my '77 Camaro, I put the GM '86 Corvette factory aluminum heads on it. That year 'vette was TPI, so no heat crossover was in those heads. Even so, with the aluminum intake and elec choke OEM replacement 9895 Holley, initial cold weather starts were "different" than with the cast iron heads, same aluminum intake, and carb. A bit more "cold natured", as they say. But the NGK Iridiums helped a bit. I expect with a cast iron intake, it'd take longer before things worked right, in our prior N Central TX climate.
As the B/RB engine has no other heat coming into it, only way the intake can receive heat is directly from the attachment to the cylinder heads and the exhaust crossover passage. Regardless of the type of choke on the carburetor. Until the thermostat opens and warmer air comes through the radiator and onto the intake manifold . . . the intake manifold will remain unheated by other means, unless there is some exhaust heat via the crossover.
Just some thoughts and observations,
CBODY67
