installing screen under Duster's air vent

How will you get screen or anything else in there ?
There is a Mustang that somes to or local cruise-in that has a piece of clear plexiglas over the cowl vent. Aeeched with screws. I've never talked to the owner. I assume he doesn't use heat or a/c.
And about the debris coming out those swinging vent box doors, I had a idea to make a register like vent to replace those doors with a screen included. Maybe even incorperate the pentastar shape in its openings.
Someone else can run with that idea. I've got enough on my plate..