Air Vents Pouring Water!
There is only a 1 to 2 inch lip at the top of the vent intakes. Next time don't put as much water into the grill as you did.
As for keeping the drains in the cowel open, since we are not mind readers I'm going to assume you have a 67 dart convertible. There are drains built in on either side of the cowel visible when the fenders are off. Make sure they are open before you turn on the hose.
On another note. You might have rust at the bottom of the cowel at the vent openings OR anywhere else up there that let the water in.
Two people and a light trickle of water can help find where it is comming from.