I paid a visit to my car at the body shop today, and with it up on a rotisserie now it's a lot easier to see the codes on the bottoms of the rocker panels. Attached below is a shot of the codes on the passenger side of the car. The driver's side is similar (with the same big "76 Z6") except the date code is "8 26 D2".
Just thought I'd post this for future reference...