I have used Factory 16:1 boxes in cars for years. My opinion is they’re excellent. Smooth, fast steering.
If you have 15° of play, somethings wrong. Not clear what you mean by adjusting the steering box tighter and tighter, but I assume you mean you’re adjusting the sector shaft gear mesh. Most probably either the bearings are not adjusted properly, or it was a bad rebuild and you have worn parts.
Attached are the service manual pages on how to adjust the steering box. You need to follow these directions carefully; you notice that the torque ranges for the bearing adjustment is narrow. You need to use a torque wrench. You can’t do this by feel or you could damage the steering box.
If the box is in decent shape, and you can get it adjusted properly, I think you’ll find a massive difference in performance and feel.
Good luck. Take it slowly and carefully and hopefully you’ll get something that’s fun to drive.
Robert

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