Displacement is up allowed up to 560ci, except the Ford 385 series which allows up to a 620ci displacement.
Running 9s on stock width bias-ply tires is incredible; there is no “but he just” anything. It’s an impressive feat that I doubt many readers here, yours truly included, can pull off.
He’s running 9s on old school bias ply street tires. That’s impressive.
No wheel tubs, no slicks, no forced induction. Just displacement and driver skill. That’s impressive.