Bob, my '65 Barracuda does not have elongated slots in that area as does yours. Instead of slots, mine has 4 round holes (maybe 1" dia.) in that center area. They are plugged with round plastic caps which snap into the holes. While mine has the same plastic covers as yours in the corner areas, there is no plastic cover for that center area other than the plastic caps I describe. The caps are solid with no screens. That center area on mine is painted interior color.
As a side note, I also have two '66 Barracudas that show that area being the exact same as my '65.