I would get 1 of each. People drive these cars because they want to. Even competently rebuilt transmissions can be had for not much money which may be more than the car cost - but so what? You'll have a car that you like driving.

The rear window at most will need the regulator lubed or replaced. Get the motor and regulator from any 126 body ant it will bolt in. Regulators are specific to the door. Motors are side specific but may be changed if you happen to have the correct part. There were motor and regulator changes which is why you need to get the entire unit.

The AC will take work but there is lots of info. I expect that a "simple refill" won't get it. It leaked for a reason. My mental calc says $600 in parts to convert from R12 with new, modern compressor. I used the SWAG method of estimation based on threads seen here.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.