Putting heat and a/Putting heat and a/c in a kit body that was originally designed for an air cooled engine is a challenge to say the least. 1st find a unit that has a heater core and ac evaporator that is compact enough to fit under the short dash. Then figure out how to duct the air "Dash, Defrost, Feet ". I took the unit from the donor car and sliced a 5 inch wide piece off the end retaining the flaps and controls then enclosed the side. Next Modify the unit to match the new duct box. Make your Duct box fit the defrost vent and modified unit. Then mate them together.