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

Trevor B said
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)

If you are saying that you filled the intake plenum:
Well since an intake valve is always open somewhere, you would have filled at least one cylinder with water, and water gets through the ring gaps pretty easy. To make this test accurate, the rocker shafts would need to be backed-off. Or if you set it up right, maybe just one side.

But if you filled the stat housing, well then, you may have more than one leak-source. This minor one, and the major one that must have had something to do with the now-removed timing cover.I would be scrutinizing that puppy pretty closely.