89 chevy k5. Bed is rotted out. Pulled out the rear bench and the bed. Under the front part of the rear bed (what the bench seat bolts to) and the bed bolts to is a piece that goes from one side of the blazer to the other. I can't find this part or a description of what it might be. If it helps, the floor pans behind the front seats butt up to this. Thanks in advance!