If I understand the above discussion correctly, somethiing is amiss. The number on the cowl tag is the Fisher BODY identification number. The number on the VIN is the VEHICLE identification number. They are never the same. I recommend two things: 1. Get Jerry MacNeish's book entitled "The Definitive 1969 Camaro Z/28-SS396 Fact Book" and 2. contact Jerry for help in certifying the car is correct. See www.z28camaro.com
Jerry has been a very big help to me and will tell you that the fraud on these cars is out of control. Late last year, I placed a deposit on a full frame off restoration, numbers matching 69 Z/28 on eBay with the condition that Jerry certify it. Jerry travelled to the seller's location to inspect and called me to say that he couldn't find an original part on the car. Saved me a ton of money!
Finally, the Z/28 has a four leaf, multi-leaf spring. Best of luck!