I've owned this 4bngr YJ for couple years now. I'm starting to collect items and add to them to the YJ. I've picked up this Smittybilt rear bumper for a TJ. The mounting locations are the same for my 94 YJ. I know the rear portion of the YJ's frame tend to rust out from the inside. The rear bumper is not enclosed so I cut holes in the rear crossmember and the bumper mount so that when I wash out the frame, the debri will flow out as well.
Did similar to my TJ years ago when I added the Tomken rear bumper to the TJ. TJs have a 'drain/access' hole in the bottom of the most rear portion of the frame. However, I've added the angle support brackets for the ears of the TJ frame so the drain/access hole is little constricted.
For the YJ, I welded the 'wing support plates' in.