The cowl vent slots at the base of the windshield is a great place to pick up high-pressure air - same place where GM-style cowl hoods and NASCAR cars pick up their carb air.
To keep a flat hood look, you could route hoses from both driver and passenger ends of firewall above the pinch weld to a ramairbox-type air cleaner housing. I've thought about this and may do it if I go with a powerbulge hood on my '69 Dart. You'll want to keep your hose connections above the floor of the cowl so any rain/wash water will keep on draining to the ground rather than running through the air hoses into your carb.