Mike,
Yes, they are the vehicle order number VON. It is just a six digit number. The specialty cars are well documented as to which block of VON they were assigned. The attached list was posted out on Moparts some time ago.
As for all of the other VON beginning with 0, 1, 2, 3, 4, or 5, I do not have an answer for you. I too am curious.
D
