I did poke a screwdriver up the plenum holes and the one on the passenger side was plugged. About a pint came out of it. Also my hog troughs both have 1/8 inch holes on the bottom near their rears. The driver side was plugged and some water came out of it. We will do the hose routine next, thanks.
When I leave my 63 Avanti outside and it rains, I get Lake Avanti on the front floor pans. Could the air/heat vents be leaking into the cab? Where are the drain holes for the water than enters the grille in front of the windshield? The windshield does not show signs of leaking, it was installed with fresh weather striping just two years ago and I keep the car in a garage for obvious reasons. What else should I be looking for as a source of this flood?