I believe you meant to say "Dupli-Color" rather than DuPont.
His original engine color was Chrysler red. I used Rust-Oleum Industrial International Harvester red on my '69, which is a bit more vivid than the original color. Blue didn't start as a low-perf engine paint color until 1970, and went across-the-board in '72 including the few MY1972 440 Six Pack engines built.
Chrysler Industrial red is a pretty good match to heat-tinged and faded original paint, but when brand new the red was brighter. The Axalta (DuPont) code for 1962-'69 red engine paint is 5092D; the PPG (Ditzler) code is 2136. At least, that's what the specialty restoration industry uses and sells for big bucks.