Nothing needs to be the same
Since the U01 file names are unique, and if the volume labels are also unique, adding the files and forcing the re-index is all you need to do.
When you select files for restore, Backup Exec will scan all mounted tapes to see if the one it needs is ready, if not, it will prompt you to mount the correct tape by Volume Label. DLT00001 or 1st Friday, or whatever your naming convention is.