I have no idea whether the bodies were cowl-tagged at Plant 21 or later at Fisher-Norwood, or both (re-tagged later); the fact that nobody seems to know anything about the Camaro Pilot process at Plant 21 or Fisher-Norwood shows the virtually nonexistent communication between Chevrolet and Fisher Body at the working level. Our nuclear submarine program should have had security that good.
Here's a personal example of the working-level relationship between the two Divisions. When I was a Production Foreman at Chevrolet-Willow Run in 1964, my Towveyor line had at least one full line stop a day for baked sealer in a weld nut preventing installation of an engine mount bolt. After complaining about it many times to our Chevrolet Inspection Department with no results, I took it upon myself to go "through the wall" to the Fisher Paint Shop to find the source of the problem. I found my way to the Sealer Deck, and to the operator who was occasionally wiping off his sealer brush on my weld nut; I described to him the line-stop problem that caused, and asked if he could wipe off his brush elsewhere. He understood, and said he could do that, no problem. I thanked him, and headed back toward the Chevrolet side, pleased that I had solved this apparently unsolvable problem with ten minutes' work.
About the time I found the door back to the stairs to Chevrolet, I was accosted by the Fisher Body Paint Shop Superintendent, who was obviously madder than hell - he demanded to know what I was doing up there, and I told him I had just solved a line-stop problem. He said, "Don't you know you're not allowed on this side of the plant? You don't belong here, and you don't talk to any of my people - all you Chevrolet a**holes need to know is the body comes up here raw and goes back down shiny, and what happens inbetween is none of your damn business - now get the hell out of my Paint Shop, and don't come back."
As I walked back to my line, I wondered how ANY problems got solved between Chevrolet and Fisher Body. About an hour later, the Chevrolet Production Manager (essentially the Chevrolet assistant Plant Manager) showed up and tore me a new one over being caught on the Fisher side of the plant, and said he'd fire me if it happened again. That philosophy is why nobody at Chevrolet-Norwood knows anything about the Fisher Body-Norwood portion of the Camaro Pilot program.