I am tired of this clunking sound from back end

[AnlaufJohn]

I finally have Lucy's Limousine back on the road and during a long drive last weekend, I felt and heard a clunk from the back end that occurs when turning left or right, after a change in forward movement, say coming to a stop.
The parts I have replaced over the years include:
both trailing arm bushings, stabilizer bar bushings, drive line carrier bearing and inspected the inner gears of the differential.
I doubt the shocks are making that kind of shift, I mean this movement affects the whole truck. It is almost like a short power slide without the power.
The u-joints were inspected when the carrier bearing was replaced and Mike is the drive line guru in town. I trust his judgement.
The bed has new bolts holding it to the frame.
Braking does not affect, but acceleration does.
Moving from a stop, either fast or calmly, and turning, will cause the noise and jolt.
Any ideas on where else to look? Everything seems tight where needed and loose and movable where movement is needed.