[Overdrive]

On the old radios there was a small area (rear left side of the unit, I think???) that would ground out to a corresponding location in the dash, letting the car know the radio is there. No radio, car panics. I can't remember if it's a piece of wire on the radio and a piece of metal on the car, or vice versa. In any case, trick that part of the car into thinking the radio's still there, and the alarm will stop acting up.

Sorry if that's not my most helpful comment ever, hopefully someone with more experience and a more fully functioning brain can elaborate or better explain. I need to go track down some caffeine.