that's the "standard" heater in my '58, the defrost hoses come out at the end of the top left and that lever with the black knob controls a flap to direct the air to the floor or to the defrost .... yes, you have something missing, where the 3 screw holes are in your end view picture, but I'd have to study mine a bit to see what - for one, there should be a sheet metal bracket there that attaches to the lip of the dash
Bill
