I pulled everything out of my car, but once again it's not going to be driven on anything but clear, sunny days. I have no roof, no window glass or mechanicals, no interior or anything like that so I just tore it all out.
If you might possibly drive the car at all at night, in the rain, any time that the windows might possibly fog up it's worth it to keep it just for that one time that you will need it.
I'd say that between all of the components it's between 50 - 100 lbs (closer to 100) that you can shave off the car. (This includes heater core, vents, vent pulls, ducting, heater controls, blowers etc.).
It is a worthwhile place to look for weight reduction...
But, only If you absolutely won't ever need to unfog your windshield.