So today had some time to finish the differential installation and test drive the bird. No more noises from the differential and a very comfortable rear suspension.
With the weight on the wheels, the rear suspension clappers are much more closed than they where before (the vertical clapper bolts and rubbers are not installed). It all drives very well, i only hear some noise from both clapper ends touching each other when the bird comes down after a traffic bump. So at least some rubber should be between the clapper ends to prevent this noise.
1958 T-Bird "Trovão Rosa" - "Rose Thunder"
Thunderbird registry #61670