If it's only when you turn left, it may not be the internal gears of the steering box.
How old are the steering components? I would check to see if there's any excess play in the tie rods, pitman and idler arms, steering coupler etc. You should also check to make sure that the steering box itself isn't moving around, the bolts that hold the steering box in can loosen up, and while it's not as big of a problem on E-bodies I have seen the welds on the steering box mounts crack at the K member and allow the steering box to move around when turned.