GX5 was a gx model, hence a GX grille. The difference is the GX5 badge. The 'S' center ornament was fitted to all 1972 JDM coupes (including DX and GL)
From the 1978 Datsun 1200 factory service manual * Mid-1978 started using the two-wire room lamp (diagram shown here) * 1971-1978 used the one-wire room lamp, with no option for a door switch (see Room Lamp Wiring)