It's still not known how many Z-11s were built - somewhere between 50 and 57 are the numbers commonly used. The owner believes there were 50 built, based on a shipping document from an engine plant showing 50 Z-11 engines shipped to the Flint Assembly Plant. Zora Duntov and his group of engineers developed the 427 Z-11 engine and body package for drag racing. The Z-11 427 engine was the first 427 cubic-inch production engine offered by Chevrolet in a Regular Production Order (RPO) car. The base price of a 1963 Impala was $2,774. Adding the price of the RPO Z-11 option of $1,240 brings the total price just over $4,000, not including destination charges, taxes, etc. As the drag racing wars continued to escalate, so did the efforts to find ways to win. Lighter cars and bigger engines were one quick means to an end. For Chevrolet, one of their attempts was the Impala Z11 with a modified 409 engine. In 1963 and 1964, the Impala was could be fitted with various types of engines with results ranging from 340 to 425 horsepower. The Z-11 was devoid of heaters, radios, sound deadening insulation, and any other non-essential items. In total, there were only 47 examples produced and even fewer exist in modern time. Source

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