The stock north American grilles used 1/4 turn screws whereas the SA
grilles use studs or attached pins that push into those old receptacles.
  I've read where some have had to pry to remove the SA grille and are
concerned about breaking it.

I found that I could insert a screwdriver shaft between upper and lower
parts of those receptacles and gently pry them apart to the point where
they securely hold the grille but prying the grille off isn't necessary.
  Mine now pulls off with just the right amount of resistance.

Mike