There are several different noises. The axles clicking in the back are not normal, and you can recreate that noise without the clutch. When you get on the power, and here a click click ( one click out of each side of the rear), that's the axle issue on early built cars that the spacer fixes.
Real low speed parking lot type driving, sometimes turning a little bit... popping the clutch in and hearing some clunks... that's the normal driveline slack. The G80 LS diffs add to it a bit by adding a little drag during turns as the clutches back there are slip/sticking. As the LS additive wears out, it can become more noticeable.
Change the rear diff lube, do 10 low speed figure 8's in a parking lot, and it often makes low speed turns less clunky/jerky when popping the clutch in. Every gear in the driveline has to have a clearance. When you release the clutch, your taking the load off the driveline quickly and the clearances can clunk. An LS diff that the clutches are dragging a bit from the additive wore out, can put a little more bind in the driveline that really clunks when you push the clutch in.
If your car has gotten annoying clunky in low speed parking lot type driving, try changing your rear diff lube and do the 10 low speed figure 8's.