[markjohnson]

The mysterious ZL-X. I believe musclecarkid is correct about the 026 cylinder head being the correct ZL-X cylinder head. I had set on a motor about 15 years ago with '1971' casting dates on them and had always wondered what their original application would have been. In 1971, the only rectangular port cylinder head being used for assembly line production was the '074' aluminum head on the very rare 1971 LS6 Corvettes. I just concluded that it must be an over-the-counter cast iron, open chamber, rectangular port cylinder head used for crate engine or even a service replacement if someone wanted to use cast iron heads on an L-88 motor in marine application. The 026 was the forerunner of the common 990's and 188's that would be used on LS6's and LS7's for the next couple of decades. By the way, the 427 I had these on was really a runner!