Very interesting thread guys. So can we safely assume that both body color and black are correct or is the answer black? I have to say that I bought my first GTO in 75'. It was a 66' original paint car. I don't know the plant it came out of but when your 17 you don't give a crap where it came from

The extensions on this car were body color. That also goes for the red 66 ragtop I bought in 76', body color. I know both of these cars were original paint. Every other GTO I owned were repaints so I can't speak to what those extensions were but they were repainted body color.
Interestingly enough, in 89' when I had my 67' ragtop repainted the original color, the shop painted the extensions black!

I thought they simply screwed up and for a while, I was pissed off. Now after reading this thread I'm not so sure....
Here's a pic of the 67' rag with black extensions after the repaint. Can't see them but the blend with the grill surrounds was nice. The other pic is my 66 ragtop which had body color extensions. Don't know if 66 was the same as 67 when it came to the extensions because the header panels were different.
Cool thread....one of those things that make you go hmmmmmmmmmmm..
Breaking news: I just got off of the phone with a member of my car club who had purchased a brand spankin' new 67' GTO back in the day. He was certain that the extensions on his car were painted body color. He is gathering his old photos to see if there were any that proved or disproved this. I'll keep you posted on what he finds.