I own a 79 safari and I know your pain. My fridge duct was almost completely gone when I started my refurb. I chose to seal the cabinetry really well around the void that is behind the fridge so that the gas has no possible other way to escape than through the vent. I would advise around the windows to use an epoxy to fix, sand and paint. Good luck. Most of the original stuff in that year was cheaper than cheap luan and extruded alluminum. Better off building your own for sure. On a side note, I was able to keep the unique overhead compartments by adding some interior bracing in spots, and I am glad that I did. I just posted some pics on another thread if you want to check it out.