Hi Rani,
I will tell you about my '72 Plymouth Valiant. It is a factory radio delete and there is an empty space where the speaker should reside. On a nice sunny day I can see sunlight channel through and it lights up the area behind the heater control levers. So no speaker block off plate was used on my car.
It does have a plain black plastic radio block off plate where the radio would be.
The other interesting thing is the right fender was never made with an antenna hole. Just a smooth topped fender and probably fairly rare compared to the volume of A-body cars they made. Im sure ,though, if you would have walked into a municipal garage or a utilities company garage in the 70's these would have been the norm.
If you would like, I can take pics and share them!
