When you live in a mid-century home, you choices can be limited when in comes to installing a/c.
The space between the walls, if there is any, can be much smaller and the homes were constructed absolutely differently back then.
Air conditioning was thought to be an luxurious purchase and several people just didn’t have the cash to put it in… My parents live in one of these house so I know firsthand how hard it can be in finding just the right Heating and A/C unit. When they met with a local dealer in town and explain that they wanted to have some sort of a/c installed he gave them the only option that would work for them, that was a ductless Heating and A/C device that could be mounted on the wall and connected to an exterior device through the wall, at first my mom wasn’t glad about the idea because she felt that the device hanging on the wall was too new looking however when she realized it would be legitimately programmable, low-service, and could be adjusted with a remote control she decided it would be fine; They have struggled for years with installing window units each summer time and then having to take them out and store them over the winter and she was legitimately tired of having to do that… Plus, the units that they own were old and not absolutely efficient and cost them a lot of cash to run all summer. This current device would not only be permanent however would be a lot more efficient and the energy bills would be more manageable. I am blissful that they took the time to speak with a professional dealer about their Heating and A/C choices and I guess they made the best one for themselves.