Was getting terrible knock during braking and turning (mainly right turns) that was proportional to the wheel rotation speed (rather than engine rev speed) and found the left side OEM front lower control arm bushing was obliterated (see image) So I got some whiteline ones put in.

Now, since I wasnt replacing with OEM bushings, my insurance doesn't cover me installing them myself - so I took it along to a local Tyre and Suspension specialist to get them installed and the alignment done to keep my underwriter happy. After the install there was a huge improvement in handling and the knocking sound was much reduced -but it was still definitely there- both when braking, and when turning right. F*%@!

Have a couple of ideas as to what the ongoing problem might be. They may have just not torqued the bolts quite up to spec when reinstalling the control arm, or they didn't get the right specifications for the wheel alignment. I was going to jack up the car and have a poke around to see if anything needed tightening - but the new bushings have lowered the ride height enough that I cant even fit my jack underneath the body anymore!

Can anyone comfirm that these alignment values are correct for my 2004 Base model? (The text on the their print out says "2014.0.2 : Nissan : Fairlady Z : Z33 Series" Is this a typo or have they possibly tuned it to the specs of the wrong model.

 

A few things...firstly they should have inspected ALL bushings for you whilst working on the car.
If that one is knackered, it's plausible that more of them are.

When is the knocking happening, at slow parking maneuvering speeds (say up to 30mph), or at higher speeds ?
If it's low, I'd imagine it'll be the ever so typical compression arms that need replacing.
I doubt very very much it'll be a loose bolt/nut - why, because 350z

 

My bets, wheel bearing or tire. A balljoint or tie rod can also cause that

 

Definitely most clunky between 15-40mph https://youtu.be/05sB0K5k26c https://youtu.be/_lqdugulx3A
Here's a couple vids to explain. Sorry about the vertical video/ loud cicadas, it's summer here.

 

Good job on popping the videos up, it certainly helps.
As terrasmak said, it's worth checking the wheels for any bearing play, and since you can do that at home, worth a quick check.

It could still be the compression arm (banana arm/radius rod - the one that's curved heh) at the end which you cannot repair - the ball joint end.
The arm in this vid:

I've had it before whereby mechanics over here in the UK that specialise on the 350z couldn't say for sure that it was this part which was failing, and they see a lot of cars. So in the end I just bought the arms and replaced them anyway, and yup, it solved the issue. It can be tricky to diagnose some times.
Last thing you can try, as you are driving along slowly, try left foot drag braking just to confirm to see if the rattle stops (not emergency stop).