'68 318 - Coolant left in heads when removed.

I removed the heads from my 1968 318 Barracuda to take them to the shop and when I removed the heads a LOT of coolant spilled out, even though I let the radiator drain down completely. I can also see sitting coolant in the passages in the block. Is this normal? What is causing this?

This made a mess that I immediately cleaned up. I also am unsure if any coolant could have gotten in the oil. I believe the oil ports are all above the cylinders where oil would ramp down the head to the block over the cam. Should I also change the oil?