I had an original 68 Z system I sold with a 68 L35 RS/SS in the early 90's. It was taken off the first week the car was owned, it had resonators.
The 68 Z was delivered mid May 1968 and was bought by the local Mercury Marine dealer's son. It was immediately modified, 4.88's, headers, and, engine sent out to be balanced/blueprinted in ATL, maybe Nalley chev? Reported to be a wicked street racer.