odd rear suspension set up

[underkut]

While taking some recent photos for uploading I thought I would ask if anyone has general experience of the boot modifications I have , I assume it was for an old beam axle, the car has always had a standard sub frame since I have owned it but I know there was a racing history and you may be able to see that the boot floor has been modified and is mostly flat with no battery box as this sits behind the drivers seat .The boot floor then curves down towards the back seat base (if I had one that is)