I would add that certainly back in the 80s and 90s the easiest way to ID the GR was the ac that was slow speed, still in 45 wing and out of ideas
The easiest way is the GR4 has two RHWR aerials on the fin, front and rear. While the F3 only has one, the rear aerial.
In the photo above the GR4 has a doppler aerial for drift, FLIR, laser ranging and marked target seeker fairings. These were not fitted to F3.
I never saw F3's fitted with outboard pylon stores / "ballast".