Brad has it right.
Also, it is highly unlikely that someone has an "unmolested" truck engine (not rebuilt to some extent). And, as Brad posted, after 60 years, any original paint that might still be on a truck engine would have changed in shade/hue.
Blue (Blue Flame Blue) was a car engine color. It might have made its way into a truck on a special order, or after a Friday birthday-lunch in the engine paint shop?
