[JoeC]

I believe the ZLX is an all cast iron engine.
The extreme Hi po BB Chevy Engines were derivatives of the original 1967 L88 although the specs changed year to year somewhat. The L88 is a 427 cu in alu head hi po BB , LS7 is a 454 cu in L88, ZL1 is an alu block L88, ZLX is a all cast iron 454 LS7 spec engine.