Found a Cheap/Affordable Solution to replacing the Defrost Duct (s)

Thanks for posting. I did my 1964 Valiant recently, with factory heat-only box. The duct tubes are different sizes on each end, so hard to source. Any used ones would have friable fabric by now. I had a box of various new duct. I forgot where I bought it all, probably ebay. Most newish duct is convoluted plastic with no metal spring, so I was able to expand one end to fit after heating with a heat gun. I recall I also used an ABS (black) plumbing coupler from Home Depot to convert sizes one place. Sometimes, you can "screw" a smaller duct into a large one to get 2 different sized ends. Secure with nylon ties. It ain't rocket science and many approaches suffice.