1. The first one is Convoy Rubber Duck Mack Truck model kit made for Ertl Company all part are attachable this one is best.
2. The second one is made by a manufacture in Hong Kong for Ertl Company this one the shape of the truck and trailer is not correct. Video clip see here
3. The third one is Model Kit Mack DM 600 made for Ertl Company looks very good quality and shape is correct done.
For those that did not know:
"There were a total of 5 Mack's used to represent RD's truck throughout the Convoy movie. RS786LST and MACK RS700L trucks. The 1977 was the one most commonly seen in the movie, but there were 2 1972's used as well as a glider mock up and a cut-away used for close up scenes."