Just realised we are taking about a 1971 car here and not a '70.
I am not sure that you will have the same issues that the 1970 Challengers had due to the different grille design.
Basically everything you could see when looking through the 1970 grille was painted black. It was a matt black but very slightly satin. Over spray extended slightly past the area needed. They were painted my men and not robots so the job varied in thoroughness from person to person.
I am really not sure what happened in 1971 or if it needed to be painted.
If this is a restoration you are trying to get as accurate as possible you had better wait until we can find out if it needs a blackout or not.
If it were my car i would mount the grille and sit in front of it to see what I could see through it. Then paint any areas showing colour through to the front.