PPG Epoxy primer works great in red oxide.
I think the number is DP-74.
The pictures below a restored inside of a factory SS/factory 4 speed 1962 Chevy Convertible and bottom of 1962 Chevy Impala SS Hardtop. The floor pan from 1961 to 1964 had the same floor pan shape and braces in all 4 years and the floor was factory painted red oxide.
Paul
Red oxide was the norm. I shot a coat of epoxy then chose to shoot acrylic enamel (single stage) and added a flatner on my Pontiac. Wipes down real good much easier to keep clean.