Poll Engine Color
Red is "correct", but more importantly, I think it looks good. It really looks nice with Commando valve covers, if you go that way.
Next choice - race hemi orange (there are two oranges).
Another choice would be turquoise. A common color in those years.
I don't care for black engines, and blue (to me) says smog motor. Mopar started using the blue almost the same time they started putting smog control equipment on cars.