The first Z06 was actually an option package first offered with the 1963 Corvette. The package was developed by Corvette's legendary lead engineer and racing advocate Z0ra Arkus-Duntov.  The Z06 option was designed to allow consumers to bolster the 1963 "Split-Window" Corvettes performance and handling capabilities for use on the race track. Selecting regular production option (RPO) Z06 when ordering a Corvette resulted in a car equipped with some tasty options.
The L84 was the most powerful 327 available for the 1965 Corvette thanks to its Ram-Jet Fuel Injection which was an expensive $538 option. For competition, race customers had a range of options available to them including the N03 36-Gallon Fuel Tank, closer rear axle ratios and the C48 Heater/Defroster Delete (-100).
For competition, race customers had a range of options available to them including the N03 36-Gallon Fuel Tank, closer rear axle ratios and the C48 Heater/Defroster Delete (-100). Most cars equipped like this came with either L78 or the L84 with Ram-Jet Fuel Injection.