Don't paint them all with the same brush. Plenty of vintage car magazines accurately reported results. I just checked several of them: a new LS6 Chevelle in the mid 13s, '69 Hemi Chargers in the low 13s, '68 Z/28 with 4.10s @ 14.85, '69 Z/28 with cross-ram @ 15.12, '68 Ram-Air Firebird @15.0, '69 Hurst Olds @ 14.08, '68 Chevelle L78 @ 13.86, '69 Cougar Eliminator 428 @ 13.91, 69 Camaro L78 @ 14.77. The #3 ZL1 Camaro @ 13.20, a Yenko Chevelle made several passes @ 13.60.
The worst of them all appears to have been Car & Driver starting with the Ferrari GTO vs. Pontiac GTO back in '64. The Pontiac was cheated up a bit with a 421. Later on they did a "Supercar Comparison" which I don't have. Mopar refused to send a car, claiming there was no way any of the test cars would be stock. Turned out they were pretty much right.