[Jeff Lee]

As the NHRA online answer was a question about an F/SA GM A-Body, the answer was poorly written. Based on that answer, and that answer alone, I'd say a racer could put a integeral headrest seat in the car.
I'd say NHRA tech needs to re-address the issue for clarity. NHRA did not specify that a head bumper (or whatever you call those) attached to the roll bar may be acceptable, nor did they specify that a factory make / model / year seat is the only seat allowed.
And when did NHRA mandate the seat be from the same make / model / year anyways? Previously it was mandated the seat was from the OEM but did not mandate the same year / model.