66 Dart heater and air conditioning

Brittle is an understatement. If your dashboard vacuum switch is bad, I was able to order a new one from Autozone for a 1969 Newport. It worked on my 65 Dart. That was at least two years ago so I can't say if they are still available.

The vacuum hoses are an assembly. Five hoses all molded to the same connector. If your under hood hoses are brittle, you can get a new set off just about any 60's or 70's mopar. Not sure if they continued into the 80's. Of course you could also repair them with some connectors and additional vacuum hose.