The original Z28 was an RPO for a Trans Am racer, and the league originally had a maximum engine size of 5L or 305 ci. Chevrolet's entry used a 327 smallblock destroked with a 283 crank, to 302 cubic inches. They shipped with a dual-carburetor cross ram intake manifold in the trunk, which was meant to be buyer-installed.
Destroked engines give up low end torque, but can scream like banshees at high RPM. Those first Z28s would have had terrible street manners and definitely would have gotten people into a lot of trouble, because the car was only happy when it was doing illegal things.
