73 swinger rear window filller?

I've heard this called the rear deck lid filler panel. Think the package tray is on the other side of the glass, inside the car. The only way I know that you can replace it is to cut and weld. Think some of the clips that hold the rear window & gasket in place are on it. The holes you have are remnants of the little pins that Ma Mopar welded on to hold a trim strip in place. The trim strip covered the seam between the vinyl top & sheet metal. Good luck.