Here is another load for the ITTX flatcar.
While these are a little larger than the mail trucks from NZT Products, I am sure David's models would look just as nice.
Carter
Those are "collection" trucks, we used to have the trucks like DKS made and had the collections done on regular routes, but not wasn't too much of a good idea as guys would have to leave their routes to go to the collection boxes to get that mail.
Now there are dedicated collection routes, using the larger trucks that go around to all the blue boxes and businesses that ship lots of mail to collect. I'd be down for a few of these too.