'65 Barracuda Body Plugs under Rear "Mat"?

We have four holes under an insulating mat, one of which is the exit for the fuel sender wire. Two of them dump into the frame rails on either side and still another one on the driver's side just empties into thin air beneath the vehicle.

I have a photo of the mat, but not beneath the mat after it was removed. Anyone have an image of how the plugs, if any, are set up under there? Anyone know if any of the three additional holes serve any purpose? Thank you.

Barracuda rear insulting mat.jpg

under rear insulation 1.JPG

under rear insulation 2.JPG