Hello, seems like there may be rust out of sight inside the arm. The
trailing arm looks ez to replace. Remove the shock and wheel.Disconnect the
cv axel at the trans and remove the 4 bearing housing bolts. Also the
hydraulic line and e-brake cable.Pull the hub assembely out. Not hard so
far. The rear trailing arm has an adjustment slot for alignment. I would
scribe a mark or two where it bolts to the van frame. Remove that bolt and
the trailing arm is removed. These arms are avaliable everywhere ,used
(junkyard).Never seen one removed from a junked vanagon. I  would put in
new bushings in and attach the arm to the scribed marks.Good luck