I just restored a 1968 GTX and from everything that I know and found out there was no option for the flat black. My original tail panel had very little textured paint left on it. Most of the area where the textured paint was is smooth with chrome showing. My original pail panel also was bright silver textured paint and not argent which is considerably darker. I decided to go with a brighter silver color but not as bright as the original looked, but lighter than argent. I bought a reproduction panel and tail light bezels.