All these fancy coatings don't last.
The best luck I've had with headers was sandblasting and then painting with simple old (Rustoleum?) BBQ black spray paint.
We're going on 9 years and the engine in and out of the car numerous times. They still look great!
Here's a shot from last Winter when I had the engine out for a wellness check:
'63 Dodge 330
11.19 @ 121 mph
Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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