From a 40 mph roll the Mustang is able to pull a couple cars. From a lower speed roll the M3 is able to hold a slight advantage. The cars are close enough the weight of the passenger affects the outcome as well as the starting speed. Starting in first gear favors the M3 significantly on the shift. It is surprising though the Mustang was not stronger with a tune, intake, and exhaust as the M3 is basically stock although if it was a manual the 5.0 would have easily had its way with it passenger or no passenger and regardless of the starting speed.
With a full exhaust and tune we would expect the M3 to pull relatively easily. Hopefully we see a rematch when the M3 has equal mods, enjoy the videos.
Camera man in M3:
Camera man in Mustang: