Actually they are both 550 series. The fire truck is titled a 57 but it was probably built in 56 because it still has the 324 while the 57 came with a 370 engine. I have a wrecker with a 370. The parts truck in front of the firetruck has nice front sheet metal and a chrome grille to spruce up the wrecker. I am anxious to see your 860. I always wanted one, but I wound up with an International with a Cummins and have run Internationals with Cummins ever since.