WELL I'VE TRIED TO FIND AN STRAIGHT BUT FIRM ANSWER AND NO SEEMS TO KNOW THE "MAIN" ANSWER SO ONCE AGAIN I AM GONNA REMOVE MY GROUND EFFECTS FROM MY 1991 FIERBIRD
AND SWAP MY "REAR" BUMPER OUT TO AN ORIGINAL 1982 STYLE
AND EHAT I REALLY NEED TO KNOW IS DO IHAVE TO CHANGE
THE HONEYCOMB/IMPACT ABSORBER TOO???????? SOMEBODY HAS GOT TO KNOW!AAAHHHHHHHHHHHHH

 

NO i am almost 100% sure you do not.
I am putting a 84 Firebird rear bumper cover on mu 90 Formula and i wont have to.

 

The parts #'s on those parts are different,so they must be different somehow.It looks like the 91 one is more rounded on the corners.But I would say that will have to try it.

 

I'm not 100% sure about your car. But just letting you know for my car (1991 Camaro) I would have to swap the honeycomb to change the bumpers. Or atleast cut and modify the stock honeycomb to get it to fit. I'm not sure if its the same for your car though.

 

The bumper on a 92 is much thinner than the 84. I have owned both an 84 and a 91 bird. The Rear impact absorber that is currently on your 91 will easily fit under your 84 bumper. However, it will be smaller than the 84 and may cause a little problem. It wont totally fill the space in the 84 and may cause the bumper to look sagging in the middle. Im not totally sure on this but it sounds possible.


So yes your 84 bumper will work on the 91.

bill