I think the amount of cold air that you are going to get is going to be minimal unless you can put a scoop on the end of the dryer hose so you are trying to push a 12x12" opening into the 4" dryer duct. Even then, make sure the tubing is straight as an arrow. Any bend and you are cutting down on the air flow.
If I do a "RAM" induction, what I am looking at doing is moving the air box to the center of the engine bay, installing a flat filter (at an angle) and then running a U shaped tube along each side of the throttlebody and then drilling 2 holes in the body of the truck to have these tubes suck off of the void at the base of the windshield. You have a positive pressure sitting there from the air being forced up and over the windshield, the air has a large opening to come in at, and due to the bend that air would make, you don't have to worry about sucking up any rain/water either. That is my idea. A bit harder to do, but the benefits in my mind are more than enough to offset the negatives.