What kind of Idle are you running at stop signs?

I am curious, on the 225 slant, in my 66 dart, with super six and elect ignition, what kind of idle should I shoot for when I am at a stop, but in Drive.
Seems I set my idle at about 850, but when i put it in gear it drops to around 600, sometimes 550.

What kind of idle do you guys get at a stop sign?