Gutter hole plug. Let me know if want pics.
I think there are also some on the top side in the engine compartment against the upper side water channels (on the inside of the engine compartment). Me thinks.
I agree. Top of fender. There are holes in the angle pieces with the curved flanges that hold the inner and outer fender together.
The plugs in the inside rocker panels (behind the carpet) are larger in diameter.
But only on the later coupes, correct. I have never seen those before, Don says mid 74.