There were 2 exterior trim packages...
The ZJ2 Custom Exterior Package had the front louvers with chrome edges.
The ZJ5 Exterior Décor Package had body colored front louvers.
Both of these packages were available on any Nova model...the louvers with the chrome edge were also part of the SS option along with the rear panel, SS emblems and hood louvers.
You can read more details at:
http://novaresource.org/rpo_ZJ5.htm
http://novaresource.org/rpo_ZJ2.htm
wilma