Coolant in Oil

check the spark plugs for a super clean (steam cleaned) plug, it's a dead give-away that coolant is getting into that cylinder. the front timing cover and the coolant crossover passage of the intake manifold can also be sources of coolant intrusion into the crank case. or a cracked casting? cast iron is tough but the unfortunate reality is that cylinder heads crack sometimes, between valve seats and also in the valve spring seat area under the valve covers. did you retorque the head gaskets after some heat cycles? any chance a front cover bolt hole in the block had some old sealer down in the hole and blew out the casting when you put it back together?

you found the milkshake in the engine, then replaced the heads and it's still making a milkshake?

I tested the rad pressure this morning. It holds pressure and does not loose any.