Washing car water leak??

I have a 1973 scamp and when I was the car I get water leaking into the driver floorboard. Not sure if it is coming from the wiper pivots, the windshield, steering column gasket , or the fresh air vent. What are the common areas of leaking for the A-bodies. I am going to need someone to get under the dash while I hose it down but any help appreciated. Thanks