Is it possible to get my 74 Duster slop free steering

Just keep in mind, the set screw on the gear box is not meant to remove slop from the steering wheel itself. Its purpose is to adjust for bearing wear on the sector shaft, and nothing more. If that has a positive effect on the steering play, then you got a side benefit.

There is also a step by step outline in the FSM of exactly how to do it. You don't just loosen the lock nut and tighten down on the screw. There is a correct procedure.