This has been debated before in this forum, and I don't remember any conclusion being made.
The 1969 order sheet says this for the Camaro SS (Z27):
"Includes 300-hp Turbo-Fire 350 engine; power front disc brakes;special 3-speed transmission; special hood, ornamentation and suspension;
BRIGHT ENGINE ACCENTS; SS emblems on fenders, grille and fuel filler cap; sport striping and F70-14 special blackwall tires."
"Bright engine accents" usually includes air cleaner lid, oil filler cap, and valve covers.
I can clearly remember seeing a white '69 SS 350 on my hometown Chevy dealer's showroom floor in 1969 with the Z/28 style valve covers. Whether or not they were dealer-installed or not, I don't know.