Hi Paul,
Here's a Ford promo pic and even though it is in black & white it is clear that he surounds on the tail lights are Black
I also have plenty of pictures of XC Falcon & Fairmont coupes and all have tail lights with black surrounds. I also owned a factory original 1977 XC Fairmont coupe that was as per the day it left the factory including black tail light surrounds.
I would be interested in seeing any factory pics that show Chrome surrounds on XC's as everything I have and seen shows black only.
Cheers
Bruce