Where is the crack? Oil gallery pressure is higher than coolant while running but when you shut the engine off the oil pressure goes to nothing while the coolant has to cool off to drop pressure.
Antifreeze will leak through where water will not.
That crack must be fairly small.
Another question is, is the engine numbers match to the chassis? If it is the engine that came in the car, I would seriously try to get it repaired. Numbers match are becoming scarser and more valuable.
