Chevrolet Impala Z 11
In 1963, Chevrolet introduced the limited but highly influential Z-11 option on the two-door Impala. The idea behind the Z-11 was to present the best street/strip technology in one model. And the first order was to shed some weight by using aluminum panels, grilles, hoods, and fenders (via Auto Evolution).
The radio and heater were gone, and they stripped the interior of all unnecessary luxuries. Chevrolet built only 50 to 57 Impala Z-11s in 1963, and single-digit models are known to survive today. They kept the package secret, so the public didn’t know the available model.