Bitter taste of defeat! So much coolant in the oil pan.

Update:
My experiment was a success, although only that it ruled something out...
The leak was not (only) in the timing cover.
I plugged the timing bolt holes with pipe-dope sealed intake manifold bolts, plugged the water holes with 1" rubber plugs, and plugged the overflow tube on the intake with a rag. Then filled up the intake with water all the way to the top... it was dripping out the oil pan plug hole.

It was not the same huge stream as it was when the car was warm and I did the same thing through the radiator last time, but definitely leaking somewhere else.

I will pull the intake manifold now and look for evidence of gasket leaks.

(by the way - if anyone cares, the engine's water jacket, intake, and heads hold over 2 gallons of water)