What's the best engine paint for the red that's on the early slant 6s and 273s?

As far as I know there are 2 different shades of IH Red. The cherry colored on I sampled above was the early color. Not orange enough for me too. Yes, use whatever you like. As long as it isn't Hemi Orange. LOL

Sorry, I didn't mean anything by what I said. I don't know how many you sampled and many people don't realise how much the original paint fades, ages, and changes colors in 50 years.
I don’t take it personally, we both chose Chrysler industrial red. Sure paint will fade over time, but I don’t think it would make up for the difference in the oil pan and distributor in your picture. The CI red is just too red to be right, even considering age/weathering/color loss.