Got ya! I see what you're talking about. You just had to trim off the bottom edge of the tunnel. Not so bad. It's still going to be a tough job. That edge should end in a horizontal flange that sits on the surface of the pan, also spot welded to the floor. That's probably not so essential there, as long as they meet. There is a 'step' near the middle where the front half of the pan sits higher than the rear. That may be difficult to replicate. You can see what it should look like in the picture below.
Here I hadn't yet trimmed the pans across the middle where the reproductions overlap too much. I was just getting everything aligned. That's what your next step will have to be, to clamp the pans along the sides, press them up gently in the middle to get them near where they should be without buckling them upward too much where you're missing metal, and then measure the width of strips it will take to fill the gap. Actually, you might try making long 'L'-shaped strips that can sit on the pan, like 1cm along the floor edge, 2-3cm vertical, then tack it to the side of the tunnel once the pan is pushed up and aligned. Then you can pull the pan off, weld the flange strip to the tunnel, and the alignment should be right on.
Big job. I kind of miss that work, though. Good luck!
Mike