It is possible for head gaskets to leak externally, but this is very uncommon. And if he had a severely cracked block I doubt the engine would run. The only time I've seen blocks crack are when a rod tries to exit the engine, or if they don't have enough anti-freeze and the coolant freezes, expands, and cracks the coolant jackets.
Does your dip-stick ever pop out on it's own? If so (and even if it doesn't) you may want to change out your PCV valve. The intake manifold can collect oil and it will leak out slowly through the large IRIS valve in the center.