Right now I've got an 89 Firebird with the black block things on the front bumper and the rear bumper. My parts car is a 84 Firebird with the two grills on the front bumper and nothing on the rear bumper (kinda like the camaro rear bumpers) I already put the 84 front bumper on by putting the bumper honeycomb thing on first and the the bumper itself. Next I want to do the rear bumper but I don't have the honeycomb thing that goes behind it. Would I still be able to put the 84 bumper on the 89 honeycomb? Would some trimming to the plastic honeycomb thing be necessary?

p.s: whats the actual name of the plastic honeycomb thing lol?

the blue bumper is the one i want to put
the red one is the one i have on right now
the honeycomb picture is the honeycomb thing i was talking about

srry the pics are a bit old and taken on a camera phone so they might not be too good of quality

 

I did the oposite, putting an '87 cover on an 84 car. Hope it works out for you. I'd be suprised if you had to trim anything.

Impact plastic, energy absorbing plastic, absorber pad...