You'll need to specify which model Dart door panel you want. The GT had carpet on the lower side of the panel. I'm not sure if the design embossed into the 270 and 170 were different. The arm rest bases are different. The 270 and GT had chrome plastic, the 170 had interior color bases. The length of the base and pad are the same for all models.
When I was working on the 66 GT, I couldn't find a driver's side armrest pad of any color that was in better condition than the one I had. I ended up having it recovered with vinyl with "grain" that was as close to matching the rest of the armrests as we could find. No judge ever caught it.