I told him I didn't think it was a real Z/28, and that I had been in touch with some experts, and they seem to also think the same. Here is his latest reply...
Haven't checked behind the heater box. The partial vin on cowl, vin plate, engine, and tranny all match. Can you tell me what is telling you that this is not a real Z/28? What I'm looking at is starting to tell me it could be a z/28 (dz code, matching #'s, z heads, z intake, etc...). I'll look at the rear later this week, and let you know what I find. I also have a meeting to see the person who sold me the Camaro this week too. I appreciate the help and again hope you feel better.
Then my response back to him..
Email me clear close-up pictures of the front engine pad stamp also. And the trans VIN and build date stamps.
Checking under the heater box is tough. Letís start with the pictures for now.