Apparently, the debut of the 429 Cobra Jet in the '71 Mustang was overshadowed by the new-for-'71 Boss 351. Thanks to GaS Publishing's How Fast Were They? we know that at least three major magazines tested the 429 CJ Mach 1.
Unfortunately, none of the magazines could be found in our magazine library, so we were unable to verify the times and information about the cars.
'71 Mach 1 CJ - 13.40/105 - auto - N/A - Sport Car, 1971
'71 Mach 1 SCJ - 13.97/100.22 - auto - N/A - Super Stock, Feb. 1971
'71 Mach 1 SCJ - 14.61/96.8 - auto - N/A - Motor Trend, Jan. 1971