Grandfather's 68 SS Camaro.

[Too Many Projects]

Headers look like early Hedman. Hooker always welds the collector flange on, usually with one of the bolt ears facing straight down into the pavement.

The only brand I'm aware of that came white were Appliance and they would need to date back to when the car was new to 6-7 years old and have a square collector flange.
They would stand out in white.

If you left the spark plugs in while removing the engine, I'm surprised you got it out without braking a plug on those headers. Damned tight fit.