Which F-4 model? The US F-4B through F-4S models never had a HUD, just a reticle projected onto the combining glass. IIRC, the German F-4F ICE did have a HUD.
Oooops...just saw that you were referring to the in-game mini-HUD.
The radar range indicator (on the F-4E) is generally mounted slightly above and to the right of the radar display. I believe that it simply indicates 10,25, and 50 mile settings. The F-4C had no such indicator, and (in RL) depended on one glancing at the range knob's position.
The developer did not furnish the F-4 cockpits with with working flap-angle indicators. IIRC, they would be on the left side panel, ahead of the throttle quadrant.