I was preparing to replace the rear bumper cover of my 1987 Formula with a 1991 Formula rear bumper cover and tried to search the forum for an answer on whether or not it would fit. Specifically, I wanted to know if I would have to replace the rear bumper support or modify the energy absorbing structure? Unfortunately, it was hard to find a definitive answer. I imagine most mods are buried in individual build threads. So I am going to answer this question. I will try to be as specific as possible.

Yes. A 1991 Formula rear bumper cover will fit on a 1987 Formula with the stock (1987) rear bumper support without modification. The only changes needed are drilling new holes on the underside of the bumper bar for the plastic push clips which do not line up with the 1987 lower bumper cover tab holes.