340 4 barrel and 340 6 barrel: were they really UNDERrated?

GTX JOHN said
A few years later with Header/Gears/Tires he set the NHRA National
Record in Fremont = 11.88 @ 113.20 with the engine never out of the car.

Headers, gears, and tires on an otherwise bone stock 340 Demon ran those numbers? Wow. What'd it weigh? What does that calculate to, like 400 hp? That's pretty remarkable.

What gear and tire size did it have?