Power Steering is Very Sloppy

I have noticed recently that the steering in my 69 Dart has gotten very sloppy lately. I originally had the factory power steering box rebuilt by Steer and Gear (maybe 5000 miles ago). It seems odd for it to be so sloppy (more so than normal). I have already worked on adjusting/tightening the steering box (turned the adjuster about 1/2 turn), but that didn't seem to do what I needed. I suppose I could turn that adjuster some more.

While looking down at the steering and having someone turn the wheel back and forth, there is a little bit of play between the coupler and the box, but there appears to be a lot of play at the point where the steering column goes into the coupler. Is it possible for the coupler itself to go bad? I was considering purchasing a Borgeson or a Flaming River power steering box, but it looks like that requires modification to the steering column (cutting to shorten) and a different coupler all together. Would appreciate some insight on what problems people have experienced like this and how they have resolved it.