Replacing rear bumper on 2001 Step-side bed

Hi all, I just ordered a new bumper for my truck not realizing that it actually has an extra corner piece because of the step-side bed. I found an old thread about this same issue, one of the replies noted that the piece was removable, but I can't seem to be able to remove that extra piece to mount it on the new one. I tried to remove what clips and screws that I could get to, but it doesn't seem to be removable at all.

Any advice would be appreciated, I know that the step-side beds are pretty rare, I never see them here in Tucson.

 

Pics go far when helping others out.

 

https://www.tacomaworld.com/threads/swapping-stepside-for-fleetside-bed.251923/#post-6093100