Really nice runs.
I've had my Mustang 5.0 to the track a bunch.
For a bone stock comparison, here's it's numbers. Where I've put x's, I don't remember the exact numbers.
Auto 6 speed. 2011 with 3-9,000 miles on it. Paper original air filter.
DA's ranged from positive 300-1200.
60' ranges between 2.02-2.08 I just can't get the 1.9x that it should.
1/8 mile is 8.45 best at 86.xx mph to a worst of 8.65 at 85.xx mph.
Your GTO has a slight edge over my car.
1/4 mile is a different story.
12.64 at low 113.xx is my best. Slowest was 13.0x at 111.5x. DA's on those were in the 300-600 range.
While the time difference isn't much in the 1/4, or the 1/8, the speed difference is huge in the 1/4 mile.
I was thinking back to my best run in my 05 GTO. It was a 12.895 at a high 109 mph time. Bone stock -250ish DA. I never paid attention to the 1/8, so I couldn't tell you what it was. I think I might have a had a 1.97 60', but don't quote me as an exact on that number.