If it's bad enough to clunk u should be able to see the play and hear where the clunk originates. Get someone to turn the wheel back and forth while u look for slight movement of the column but not the lower yoke.
When were the rack rubber isolators last replaced? These are a weak point and u don't want them to fail underway, so if they're old I'd suggest replacing them. Also prone to crumble to bits over time is the bushing the supports the upper column.
Hopefully it's not wear in the center tooth region of the rack/pinion.