Like 95 Truck posted, easy to believe when you recognize what your looking at.
Nothing really special in performance about the '69 ZL-1.....it's the same as the rectangle port head, solid lifter cam
iron 427"/425hp engine Chevy was already putting in the Corvette and a few Caprices, just cast out of lighter material. Aluminum block and head doesn't add any power in this case, it's just lighter is all. Everybody ohh's and ahh's about the "all aluminum engine" deal.
The GTO was a blueprinted dealer performance tuned package track pack car with 4.33 gears.
Only 130 lbs weight difference, ....and the added weight of the heavier GTO is almost completely in the back of the car.....the Camaro is still nose heavy/rear light even with the aluminum engine. Traction advantage to the GTO on the limited tire, more weight on the rear tires and those 4.33 gears, get the jump in the first 60' using all that low end torque.
Get out in front and just hope you got enough jump to hold off the hard charge of the higher hp Camaro....and that's what the timeslips in the video shows.

GTO quicker ET but less MPH
Camaro worse ET but higher MPH.....just needs another 100" of track is all to blow by that GTO by a good 10+ mph by then LOL.