On 67 -69 convertibles any water that gets past the top runs to a gutter in the car that dumps into the front of the rear quarter and rocker area to drain out.
...or to not drain out when those get plugged. Got home one day in the rain and the rear footwells were FLOODED in our GTS. Quickly cleared out the garage. Removed the seats and carpet outside and cleared the drains. Then put the car away to dry...
