There are NO traces of silver paint on the front fillers on my 73. If they were painted with a silver paint, there would be signs of it left on the areas that were shielded from the elements. There were no traces of paint where the bumper overlapped the filler.
As far as the rear is concerned. It does make sence that they would have been painted before hand because the tail light buckets were painted before they were put on the car. The rear filler strips most likley came from the manufacturer painted with the argent paint, ready to be installed.
On a side note...there was most likely a color difference between the tail panel and the tail light buckets from the factory. The argent on the tail panel was sprayed either over body color, or primer. The tail light buckets were first completely sprayed with organisol black...then they were masked off and the argent was sprayed ontop of it. If you look at origonal buckets, you can see black specs showing through the argent. The accual tail panel itself wouldn't have had the black showing through.