With no bulbs in any headlights, tail lights, parking lamps, you should not see any continuity from any plug you describe to ground.Be aware that you should not use the sound feature of a DVM for measuring continuity, particularly as it will beep if there is a bulb in the circuit (bulbs have about 1 ohm of resistance). I suspect you measured continuity with bulbs in the circuit.
The only ground wire is for the constant voltage regulator on the back of the dash cluster. The entire chassis is grounded by a lead from the passenger side rear head to the firewall. There are ground wires for the front marker lamps, headlamps, and tail lights, but they are near those devices and plug into the chassis. Similarly, the license plate lamp has a separate ground wire.