ZLX question

[Schonyenko2]

I looked at a survivor (well almost) X22 69 camaro today.Was an original 396, don't know the hp rating, but was blown up early in it's life. It had what was described as a ZXL 427 installed at the selling dealer by paying over what the warranty cost of the 396 was.(not uncommon back in the day).The rest of the car was undisturbed although he claimed they changed the factory ordered rear gear 4.88 to a 3.31. Turbo 400 floor shift. Original HO, narrow rear spoiler that appeared original, and had the larger torsion rod. Was also a factory cowl induction hood option.
This question has been asked before, but I don't remember a definitive answer. What was the true story, and specs on these supposed to be ZLX CE motors. I've heard the term cast iron ZL1, but there were no open chamber cast iron heads until 71 that I'm aware of. I see nothing about this motor in Colvin's books. Explain please.