I took a rear bumper off my 89 bronco to put on my 97 f350, what a pain in the a$$. you would think that they are the same but the bronco bumper sits up higher by a half an inch or so. I did use the brackets from my f350 bumper as well but it took a good hour and a jack to tweek it into place

 

The Bronco brackets are different. I have no idea why that has to be. Couldn't Ford have made the rear of the frame on a Bronco the same as an F150?