You need to price the market on enthusiast owned Z's.
NADA/KBB reflect daily driven, minimally maintained cars with no significant aftermarket parts.
Think about it... If your mom had been daily driving your Z since 1990 and in charge of all maintenance, what would your Z be like right now?
Antihero
Putting AMS garbage, and $500 ebay wheels on a Z is like dressing a Victorias Secret model in a Walmart dress and Payless shoes. You're embarrassing yourself.