I found several of the backing plates that hold the dash to the hull missing, as per the picture. I found some stainless bolts that fit into the nuts which appear to be attached to the dash panel somehow.

I replaced what I could. I still have one nut on the passenger side that appears to be broken off, so I will look into how to go about fixing that. No rattles or squeaks, and everything still seems solid, so I'll leave it for now.

Here is a picture up under the passenger side showing the hole with the nut attached to the dash.