Well, I just got back from a trip making a delivery run in a Penske unit. It was a 4300 International 4300 with 24' box, 25,500 GVW. It's box's floor height is 50".
The two locations I pulled into had loading docks that were 'short' for me. They were both 3-1/2' or 42". Anotherwords, I was 8"...