The magazine modified the engine, like swapping the four-barrel carburetor for the "six-pack" configuration, to produce 376.1 horsepower at 5,500 rpm and 408.9 lb-ft of torque.
Those numbers put the 340 ahead of the L79-powered Corvette. Unfortunately, this is where the engine peaked, due to new emission laws in emission laws in the '70s.
In 1970, Chrysler advertised the cars using the six-pack 340 engine as producing 330 horsepower, but Muscle Car Club reports that number to be about 20 horses lower.