LOTS of noise when turning

[392 Cuda]

After an unshakeable vibration issue with the driveline, I've finally replaced the last of the original driveline from my 74 barracuda.

I now have a 392, 8-speed, AlterKtion Front suspension and Street Lynx rear 4-link, with a new aluminum DriveshaftShop driveshaft (CV front, U-Joint rear), and a freshly rebuilt and narrowed 8.75 posi 3.55 with Moser HD axles.

I finally finished this round of updates and now I have some serious noise coming from the back of the car. It sounds like something binding up
- It's fine driving straight at any speed, only makes noise when turning (but not every turn)
- All the suspension parts seem to have decent mobility
- It starts after about 15 minutes of driving, never when cold

I put 3 4oz. bottles of Limited Slip Supplement in there.
- After the first it seemed to get a bit better.
- The second and third didn't seem to do much.
- I put about 50 miles on the car through all the test drives (bottle said 20 miles to mix), I spent some time doing cold figure-8s in a parking lot after each bottle with no noise until it heated up

I'd appreciate any thoughts... Someone here seems to always know what to do.