MY FIAT TOPOLINO HEATER SYSTEM

 These three  critters are parts to make demisting/defrosting possible in MR T, my '37 FIAT "EuroRod". Top pair are the air outlet nozzles at the base of the windshield. Bottom is the fitting that slips into the stock Fiat 124 Spider heater box.

 This is the heater box, mounted inside the cabin. At the extreme top is the defrost air fixture, fitted into the heater box.

 This photo, taken from outside the car looking down through the [not yet installed] windshield, shows the two defroster delivery nozzles bolted in, at the base of the windshield.  The orange knobs cover the windshield wiper arm actuators. The wiper motor and linkage are stock Fiat 124 Spider, narrowed slightly.

The drawing shows the whole heater/defroster system. Outside air comes into the system when the cowl door on the right side of the car is opened [extreme lower right]. Just inboard is a second door, which lets an adjustable amount of fresh air in on the passenger's legs. If the outside door is closed, this door [when open] lets air inside the cabin to recirculate through the heater.
Air is directed to the top of the stock heater box, where it passes over the heater core and either out the bottom, into the cabin, or up to the defroster tubes, or both, depending upon the position of the slide controls on the front of the heater control panel.
A bit of fabrication was required, but that's part of the fun. I was determined to have an effective heater/defroster system in this little mouse, so there it is.