For your search, the 04 -08 FI Wide Glides use the same tank as the 07-10 Super Glide Customs.  They will bolt up to your FXD fine.  You will need new console, speedo and brackets, and hardware.  You will also need a new bar clamp.  The swap is fairly straightforward.  You will probably have some wiring extensions needed in the project.  I have access to some pretty good info on swapping the tank guts.  When the time comes, let me know if you want it.  A service and parts manual would be a great asset while doing this.