The screw holes was moved after the 70 model year (ok, really about 2 months into the 71 model year) to the location in the corner by the window.
It makes sense if you've had a 70 with the screw in the original position, as the plastic warps away from that corner.
74 rear panels also had slots for the shoulder belts for the driver and passenger in the same position as the ashtray.