Ya that's an international extended cab. You can tell by the door and the back window and the unmistakable windshield. The roof is a different color because of the primer. under that is the black primer. International trucks took it seriously, like they do now with their new 'pick-up'.
The truck with the extended cab is an International early to mid 50's probably a road tractor. The extended cab is actually a sleeper for the driver to sleep. The shape of the door & rear window is a dead give-away.