I have found there are 3 "ZL" dealer options. 1 is a ZL option for the LS's, and 2 for the SS's. It is a power adder option for the cars with a few body mods. I saw one of each at Gordon Chevrolet in Augusta, and they look pretty cool, but they have the same issues as every other SS adding a lot of power.
2013 IOM ZL1 #002415 Born 09/13/12 - Oracle DRL LEDs, Fog LEDs, Defenderworxs Black vent inserts
2010 SIM 2SS/RS #005549 Born 05/02/09 - Oracle DRL LEDs, Oracle SMD Afterburner LEDs, K&N Typhoon CAI, Flowmaster Thunder series axle back, Heritage Grill, Superchips Tune, Defenderworxs Black vent inserts
1983 S10 - 383 stroker (10 second monster)