Dart question

If you did, I would also suggest removing the doors on the vents, if not the entire vent structure that bolts up to the cowl. That way there's actually air to circulate through the cowl to the heater when its running.

Hopefully you've got A/C or are planning on adding it. The amount of air that you can move through those vents is pretty incredible. It's a noticeable difference opening those vents, even with the windows down. Definitely makes things more pleasant in the cabin. They're also super helpful if you want to circulate air and still have the windows up, like if you get tired of getting blasted by air from the open windows on the freeway. My new favorite trick on my Duster is to open the cowl vents and crack the rear pop-out windows and leave the windows rolled up...