[chap52]

Just like with the Model A's you can fill the radiator to to brim and as the water expands it will send fluid out the overflow as the radiator seeks it's "happy level". After it finishes that process look and see if the plates in the top of the radiator are covered with liquid. If so and it's not overheating, all is well.
If you are still concerned you could add a radiator overflow system.
Bummer about your FedEx adventure. Thanks for the heads-up. Chap