For purpose of detail, here are some pictures of an original MGA 1600-MK-II grille.



Below left is a picture of a somewhat tatty MK-II grille, but at least it shows the rear side. Notice four holes for screws in the bottom rail of the slats assemby, and two pop rivets up the center web. This is a result of the recessed shell being made in two pieces, left and right halves, those pieces having separate part numbers in the SPL.
The second picture below shows an early grille slat placed over the MK-II grille slat. When current vendors sell the grille slats assembly, claiming it fits all MGA, take it with a grain of salt. The 1500 grille slats are 8 3/4" long, and the MkII slats are 7 1/4" - significantly shorter! Definitely not interchangeable.

Find a list of assembly fasteners for this on the 1500 type grille page.