Back in about 1987 when I was rebuilding (as best I could) my '67 Monaco, I changed the upper ball joint and upper bushings on only the driver's side. I have had in my parts stash for many years a set for the passenger side, I can only assume they are identical to what I put on in '87. Below is a photo of this "NOS" ball joint (on the right) and a new joint I bought from rockauto this year.
The old joint does not have a bright finish, and it has these marks stamped on the top surface:
USA BJ6612 K 4588
The new joint (on the left) is a QuickSteer K772 (or possibly EXCK772) made in, of course, China. I note the slight difference in various dimensions. The threaded tops of both are the same length, it might appear different in the photo. The flats of the new joint do appear thinner, they come close to being 1/4 inch thick only at the center point. The old joint has a uniform thickness of 1/4 inch (better to put a socket on).