The pre-drilled mounting holes in the '06 tour pak won't line up with the holes in an '09 detachable rack (or the the rigid mount found on EG Classics or Ultras which are the same as the detach rack).
Use the holes in the '09 and newer detachable rack as a template to drill holes in the '06 tour pak bottom and you'll be able to reuse the '06 tour pak on your new bike.
Take a tape measure to a buddy's '09 or newer tour pak, or go by a dealer and measure from the front of the tour pak to the forward mounting holes in the tour pak so you will know where to put the rack on the bottom of the '06 tour pak for drilling the holes.
Good luck with your project.
Carl