rear box supports

[turner15]

I need a photo of the rear box support, where it connects to the bedside. I have a fleetside 71 but I think they all look the same. I'm rebuilding mine and don't know what I need to rebuild. (its so far gone.)

Here are the questions I have based on the photo.
A. is there a lip here that the wood rests on? If so how wide is it?
B. Is there a lip here and how does it interact with the side lip? Over lap or butt?
C. I find it strange that this big holes are here? Is the any hole suppose to be here? If so do you know why?

I included some other picts of my work. Lots of fun rebuilding the lip and inner wheel well