It's a short run, (probably not much more than a foot?) so I think #24 will be fine.
Mike, what you are looking for at the motor is #3 or#5 on the wiring diagram. Those are the two field coil wires and now of them is the culprit I'm pretty sure. I hope the wire isn't broken off where it comes out of the field coil too close to make a connection. I really want to see that old Crane working.