Swallowtail rear lid/tailgate vent openings

Hi

I've bought a nos tailgate which I am having painted soon. As the photo shows it is an early replacement lid, so it has pre-cut holes to accommodate all models. My car is from Oct '76 but is a 77 year model, so it does not have the vent openings originally. I kind of like them, but if they were never used after the swallowtail transition i will probably have them welded in for the sake of originality.. So does anyone know exactly when the vent openings was phased out?

I saw them in a 1977 GTI recently, but I suspect that was a replacement tailgate as well