Jon,
  What rack bushings?  The XJ6 had rack bushings but the XJ40 does not.  It
is mounted on by 4 bolts metal to metal with no bushings.  The only other
connections are the tie-rods and the pipes.
   If you are getting a rattle when you hit a bump, chances are it is the
shock bushings at the top of the shock absorber. You have two on each shock,
one on either side of the fender wall.  When they deteriorate, the shock rod
bangs on the fender wall.
   I forget the weight of the rack, but it is not that heavy.  Should be
around $20 shipping.

Webserve