It appears to be quite a job to replace the steering box and I wouldn't want to do it for a negligible reduction in play.
During this last year, I've been working on restoring the engine compartment of my mustang. One of the disappointing issues when driving this car was the steering. So when the engine was out, I went through all the steering and had the steering box rebuilt. The car is driving now and the difference in handling is night and day.
The steering box was the main issue as everything else was in good condition and tight. There will always be some play, but with a rebuilt steering box, driving the car is simply a pleasure and the confidence you have behind the wheel is, well, basically 10-fold.
I believe these boxes can either be a four or five turn configuration and I'm no expert in knowing the difference, but you'll want to figure this out for your application. Mine was a four-turn box. Depending on your desire for originality, you may be able to have your box upgraded when rebuilt.
I guess what I'm saying is, if you have the time and around $200 burning a hole in your pocket, don't hesitate....you'll be very happy with a rebuilt steering box. It will make all the difference in driving your car.
Just my .2 cents. Good luck.