Thanks you guys!

Let me explain the symptoms and why it was suggested to me that the housing is bent.

SYMPTOMS
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1) with the rear end up in the air, so tires are off the ground, in fact tires can be removed, drivetrain in N(eutral), I can turn the wheels forward easily, but they are extremely hard, nearly impossible to rotate backwards, brakes are not a problem since you can remove the drums and turning by axle flange produces the same result (my local shop buy pointed this out as a proof of a bent housing)

2) the rear tire thread has a wear pattern, the pattern is nice and even across the tire on the pass side, but on the driver side the pattern is off-center and towards the inner sidewalls of the tire

3) at higher speed, so around 30-40 mph a noticeable vibration is present, it is cyclical, almost like a repeated SG clutch chatter that you might get going around a sharp corner

The rear end in question is using a '741 carrier, 3.91 SG ratio. New MP clutch kit, only about 500 KMs of use since rebuilt. All new bearings. Fluid is a synthetic mix with the SG additive.

Driveshaft is brand new from DynoTech in Troy, MI...as are the U-joints, yoke, etc.

Engine assembly was balanced at the machine shop, I do not feel any vibration when revving on it's own.

What I can tell you though is that this very same housing, but a different carrier were previously used in another car of mine. I do remember having a similar vibration and back then, not knowing much about Mopars and drivetrains, I simply attributed the 'shake' to bad driveshaft (it was a stock piece), bad U-joints (stock as well) and so forth. So the housing is he only consistent part that seems to 'move' with the vibration.