JOZ,
It's been my experience that Tonawanda installed a bare steel inspection cover, bell and fork, then painted it. The degree of orange on the bell, cover or fork varied depending on the guy doing it that day. I believe the final assembly plant installed the rubber boot for the fork when they installed the linkage. All the service replacement inspection covers were supplied black.
IF you look at Pascoe's '69 Z photo, it sure looks like the cover is bare steel with a little orange overspray.
Verne