Ball joint size?

You don't have to measure like that.

Here's another "trick" for everyone.

If the thread diameter of the stud is 7/16, they are the 62-72 small ball joint.

If the thread diameter of the stud is 9/16, they are the 73-76 big ball joint.

Use a 7'16 and 9/16 open end wrench and put it around the threads.
Easy enough to do, and check that way, if your eyeballs aren't up to see the difference.