427 aluminum block

[William]

With a casting date of 5 15 69 there is virtually no chance it was an original engine in one of the 69 production ZL1 Camaros. By that date 67 had been delivered. The last two were final assembled on or about June 3, 1969.

Unlike production cast iron engines commonly built within a week of their casting date, the span between casting date and pad assembly date for production ZL1 engines was considerably longer.

It is possible it was built as a service engine assembly as several have been located. Production engine codes were ME, MG, ML, MM.