I'm partial to red oxide colored epoxy, but I've noticed that when painted, it comes out looking way too orange. I even went to a local paint distributor and had them check the various brands of red oxide primers, but they all were pretty close to a very bright, almost pumpkin-like orange. It looked nothing like what was on my car. I understand that no two cars were alike, especially regarding the shade of primer used on them.
With that being said, however--and again, take this with a grain of salt--I went though all of PPG's color swatches and picked a color that mimicked what was on my car originally. I ended up using a epoxy primer base, then went back and covered it with a 2001 Nissan basecoat/underhood color called, of all things, "Rust." Again, it may look nothing like what came on your car, but it's a very close match for the red oxide that used to be so popular back in the 1960s. It's a very reddish, muddy brown looking color, and it has none of the brightness or halloween look that the epoxy primers sold nowadays have.