This shot shows how we tied the tunnel into the rear bulkhead to help carry the loads forward in the chassis. The little bulge you see on the side is for clearance for the pinion flange on the differential! Yes, everything is extremely tight on the car and there is very little room to work with.
This shot shows a little clearer how we had to bridge from the tunnel to the frame rails. We couldn't just splay the tunnel out further as the tunnel would have then intruded into the seats. As it is, you want as much room as possible for the driver and passenger.