The factory plugs on both sides of the steering column were holes for the air vent cables. If the car was factory, or dealer, equipped with a heater, there should be a knob with a "V" on it on the right side of the steering column. There were actually 3 heaters available for the Henry J but the '53 most likely has the one my '53 has. Here's a picture of my dash, which is original.
To the left of the steering wheel, mounted on the bottom lip of the dash via a chrome hanger, is the knob with "H" on it. This is heater blower knob, and this is where it was mounted.
I would also ask if you are sure the one in your car is a factory issue heater? There was never a factory HJ heater with a light on the dash. Since the Henry J did not come with a heater, many of them had after-market units in them.