What is an iceberg?

What is an iceberg, yeah yeah, big block of ice. What i am referring to is the fact that about one ninth of the total mass of a berg projects above the water. So to cut to the chase.....what you see on top is only a small part of the whole thing.

So, how much metal should be removed to get rid of that rust ridden piece of steel? about this much

The section of floor was removed because it is easier to replace it with a new flat piece. The holes for the accelerators weren't touched so I will be able to refit a new one in the original position. I am still trying to keep the original look inside the car