In 1959, Chevrolet finally gave the Impala its own model line instead of treating it as a Bel Air option package, and backed it up with a lowered, widened body sharing sheet metal with Buick and Oldsmobile, horizontal tailfins, and an engine range topping out at 315 horsepower. A year later, Chevrolet toned almost all of it down. Read on to find out what changed, and why some Impalas from this era were hand-built in Australia.