Bjorn is right, it will drain (or the water will flow) down the cowl, and down the side, into that area, and there will be a drain slot for the water to run out, But, the kick panel vent is shrouded as it goes into this area and is about 4" - 5" deep, and then has a putty type of sealant to seal the kick panel vent area from this open area behind the fender...

So in most cases, you will be getting water inside the interior from this now open area. Weather it's splashing, or just flowing enough to get some water in there... it's bound to happen.

Try to get some of that type of sealant, and a sheet of plastic, and put the sealant around the inside of this area and see if you can temporarily seal it up... or at least slow the leak down?

But I'd say chances are good that this is the cause of the leak...

Brett - 67 Drop Top 455!