Dumbfounded about the clunking linked to both individual rear wheels.

Hey, I have a early model excel panelvan making a clunking noise consistant on both sides on every rotation of the wheels wether driven with load or spun in he air. Ive only replaced right rear bearings to find no noise when spun with no load but clunks on the ground. What are the chances of all rear bearing flunking out within 100m of each other? Also ive read up and alot of other people have had drum brake noises without a problem with the drums but been shocks and control arms and whatever else. Oould I be looking in the wrong place. Thanks a million