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1974 is the first year that the rear bumper cover ("light panel") bolts on (see Post #3). The part you show in your link would require fiberglass work to install, so it's really more of a post-accident repair panel, like a replacement fender.
Of course when you say removable most would not think first of that panel, since it will need to be bonded in and typically require some bodywork to fit it properly.