Recently we took all the radiators out of the house, and I was surprised that I was able to get 5 foot radiators into the car - front seat forward / tilted, and was able to get to the recycling centre with radiators + other junk without any problems:
There was one six foot radiator which would not quite fit in. The day after taking the radiators to the recycling centre, travelers came around and knocked onto the door for the big radiator!