Hi colin-s and welcome to Fordforums.
About your 3 queries, it's obviously hard to pine point the problem, but here are my guess of what the problems are:
1. With 43k I would highly doubt the sound is from the tappets (correctly speaking hydraulic lifters). Especially since you mentioned that it's on the decellerating part when you give the engine a rev. Does the engine do it when it's warm or at operating temperature?
2. That clunk you described is definitly from the ball joints, go to ford and demand a new set of ball joints with the right grease in them. Apparently early build AUII's had the wrong grease in the ball joints causing them to breakup in hot temperatures hence the knocks. I would guess if these knocks have been going on for a while the ball joint would be worn as well.
3. I would check that the steering rack bolts are secure, they tend to come loose on these models.
Like i've mentioned these are only my suggestions from your description so i may not be 100% correct.
Hope this helps.
Motor May 2001 Quote: "Believe it or not, there are actually a bunch of weirdos out there who reckon a six cylinder is the dux gutz. Bugger it: I'm one of them" :s5
AUII Late Ed XR6 HP T5 Venom- Full Tickford Body Kit, 17in Wheels, Herrod Bi-plane Spoiler, Momo Steer/Gear, T-Series Interior Options, Premium Stereo and a very light-tuned 4.0L I6
(FPV-Tickford Club of NSW Member and Co-Founding Member of 3FB Inc, Ford Forums Food Bandits)