Same problem as always. Coolant in the oil.

How fast does it drain down? Is it where you can look in the rad cap opening and see the level drop, or is it a slow weep?

None of your plugs look odd, so it sounds like it's not going through the combustion chamber.

If it's draining FAST, it's not likely a cracked head unless you can visibly see the crack. If the settled level in the radiator is below the heads, it's not the heads.

I don't know which head gasket you are using. We had a head gasket that the embossed area for a water hole was made too large and allowed water to enter the valley. It wasn't a fast leak, more like a weep, but it was still there. Manufacture sent a new gasket that was right the second time.

Everyone has there approach. Mine is to inspect everything that sounds reasonable before spending money on things that may/may not be the root problem. It sounds like you have a mighty large hole in your cooling system, timing cover, intake surface/gasket crush, head gasket.