Steering rack adjustment

[Themoog]

Has anyone adjusted the preload or replaced the bushing with a kit to stop clunking from the front end?
I've been chasing a clunking / knocking from somewhere in the steering that feels like it's coming up into the column and I think I've narrowed it down to either the inner tie rods or the rack itself.
I've had someone rock the steering wheel side to side while I lay underneath and there is definitely a knocking.
If I shake the tie rods up and down or side to side I can't feel anything so it possible that they can wear in the horizontal plane only? With the wheels off the ground I can't feel any play by rocking them at the 9 and 3 o'clock positions.
Failing that it must be the rack itself that's loose somewhere as I've replaced the steering shaft and column bearings already.
Thoughts?