I did it with a 71 140 about 12-14 years ago. At that time R 134a had yet been introduced so I didnt need to concern myself with installing parts which are now used to convert an old R 12 freon system to use the new stuff. If you choose to stick with R 12 and not convert, the freon will be mighty expensive. On the other hand, R 134a is relatively inexpensive but then you should get advice on exactly whats needed to convert.

I was able to remove everything needed by scouring several cars at a wrecking yard. I took along paper and pencil to make notes about where each component was installed, plastic sandwich bags for small parts and brackets etc., masking tape to label everything. When removing the thermostat, be very careful undoing the capilary tube which is fed through the condensor which is installed where the glove box is now. Anyway, if you should break the cappilary tube you wind up buying a new thermostat. Also, careful opening all the connections; for example between the hose and the evaporator.

Once you get everything installed, which is not difficult, you will need to have the system purged, dried, install a new dessicant can(thats the long black cylindrical can with two hoses connected to it) and add refrigerant. This takes specialized equipment.