[rynoshark]

Per annotations on Chevrolet's internal NPC "Notice of Production Change C69-39" documentation, the first date that a ZL1 engine assembly was available for production installation at the St. Louis Corvette assembly plant for a Corvette with option RPO ZL1 was December 9, 1968.

Further, the separate internal Chevrolet document "Notice of Production Change C69-39, Supplement 1" indicates with annotations that the first day parts were available for building a Corvette with a M40 automatic option for RPO ZL1 was also December 9, 1968.

In the absence of any other internal Chevrolet documentation, the data from these NPC documents indicate it appears that on—or within days—of December 9th, 1968 the first Corvette with option "RPO ZL1" was built. Further, based on this documentation, any Corvette built prior to that date which may have had an aluminum ZL1 type engine installed would not have been with the "RPO ZL1" option code. Given the Daytona Yellow ZL1 is well documented to have been built in September 1969, these would be the two bookend RPO ZL1s.

NOTE: All internal Chevrolet documents referenced above have been uncovered at GM's Heritage Center within the last two years.