billboards where not installed at assembly plant. they were shipped in the trunk of the car for the dealer to install to keep from getting damaged during shipping. as to the maker light housing would have been painted body color from the assembly plant. there is evidently no "correct way" to install stripes, all dealers were not constant. however, IMO , the marker light housing would remain body color and simply removed for installation of billboard and the housing would help hold the stripe in place. most likely you might find evidence of the stripe on the inside of the 1/4 panel where the opening may have been "x ed out" and folded over. you may check your inside door edge also. personally I would put the billboards on anyway, awesome look.
From what I recall on the subject, billboards were initially installed at the factory, hence the "black and white marker housings", then early into production, issues on the line regarding proper install and time allotment, plus dealer feedback from customers not wanting the stripes on the car led to them being shipped with the vehicle for dealer placement, dealers weren't concerned or knowing of the "correct" marker lite color/stripe coordination, so the original marker was re-installed whatever the body color was, hence the battle over some that proclaim their body colored non white/black side markers are original to their billboard equipped car...
I guess one would have to have been there on the assy line/dealer operation to have known for sure...
