My rear bumper on my '85 Delta 88 is rusting from the inside out, and it needs replaced. Don't need anything but the chrome.

 

That's a pretty common problem. Should be plenty of those around in the boneyard. I believe the 80 - 84 Ninety Eight used the same bumpers. You might be able to expand your search using those models too. Good luck with your search. BTW, chances are that if you get one used, it will come with the plastic trim and guards.