Coolant overflow capacity?
Real world experience-
My 73 318 Satellite did not come with an overflow/recovery tank despite coming with AC.
(It's also got a fixed fan, which is odd to me)
If I run the AC, it will get hot enough to purge some coolant, and after a few drives, the coolant level will be too low.
I added a 1 quart heavy plastic travel cup but found it would over flow when hot, and eventually leave the coolant level too low.
I found increasing to a 48 OZ container solved the issue.
Be sure the hose from the overflow goes almost all the way to the bottom of your recovery tank (effectively creating a "closed system" if kept below the water line in the tank), and that the radiator cap is a "two way" vent.