Shelby Cobra Mustangs.. the last years of the 1960's had interesting tail panels, rear air spoilers, tail lights, and exhaust tips. Not my favorites, but good

 Above is a 1969 by license plate (ZLR _ _ _ would have been registered in Aug or Sept 1968)
I think the dual center exhaust tips are likely originating on this model Shelby Cobra Mustang, I can't recall ever seeing a car before it with the dual exhaust in the center, instead of spread out to the far corners... and new cars still mimic this, like the Hyundai Veloster

1967? I think.