What's up with my trailing arms?

[jayoldschool]

After looking at many pics of projects in this section, I realize that there is something strange going on with my truck's trailing arms. Mine have space between the two halves. Didn't realize this was not correct. Also, I thought that the stuff in the space was just rotted wood debris from the decayed bed, but after getting a closer look with the bed off, I can tell it is metal. I have no idea why that would be in between the two halves of the trailing arms.

Not sure what to do here...

Here are the scenarios that I can think of:
- do nothing
- try and knock that strange metal out of there and squeeze the halves back together, then bolt or weld
- start shopping for a pair of arms

Thanks for any thoughts.

Here's the pics: