Dash vents question

I am waiting for my new dash vents to arrive. My question is: can the windshield be in the car when I install the new dash vents? I was hoping to get the windshield in the car this week end, but I don't want to screw my self over when it comes to installing the dash vents after the windshield is in.

Sure they can. It is easiser to install them when the dash is on the bench but the windshield does not obstuct installation or removal!