Before you make a final decision, I would recommend you do some more research on what kind of primer was used on your car. I suppose anything is possible, but I've never seen red oxide primer from the factory during that era.

 

We restored a 70 SS396 that came with the same red oxide your talking about. We used a catalized two part paint mixed to match the red oxide. Any paint supplier can set you up with it.
Roger

 

Most every major paint mfg. still offers a red oxide primer. Unfortunatly most of these are acrylic lacquer, which is not recomended under todays bc/cc systems. There are many 2k primers out there that can be tinted with up to 10% toner. Your jobber should be able to tint a 2k primer or sealer to your specs.