Thank you for posting the pictures of your exhaust system and YouTube sound clip. Your car looks and sounds great! This is the first time I have heard a ’69 Z28 with stock exhaust and resonators.
I just played your YouTube sound clip side-by-side with my system and they are very similar. Your system with the resonators is a bit quieter than mine without resonators, but not by much. If we were to run our cars side-by-side, I am sure the tone would be more noticeable.
My idle characteristic is slightly different due to my recent motor rebuild and cam selection. My car is not a numbers matching Z28, and has a replacement "DZ" engine, so I decided to update the valve train to a full mechanical roller Comp Cams #12-770-8, "XR274R. The cam's 110 deg lobe separation, lift, and the intake and exhaust duration allow for very nice and usable RPM range of 2200 - 6200. I am very happy with the power this cam provides and it is very drivable. My goal was to retain the stock mechanical lifter sound, and keep the stock valve covers, so the engine look and sounds very stock.
Again...great job with your car!