Use late model (rotary) underhood and original underdash unit for inside the car. An orginal underdash for a 1965, runs about $200 with the mounting parts. Underhood use more efficient compressor, new hoses, and better condensor. LMK if I can give you any more info.
I am very happy with the tech support from Classic Auto air. I would definitely recommend them. I have heard good things about Vintage air, but I don't think they have "original-looking" units (all underdash/heater stuff).