Normally a RebuildBS takes only few minutes.
For large disks a little bit longer.
Except if Rebuild BS doesn't find any path to a file system.
Then it will search in each sector for your MFT.
Your partition is not PC/Intel standard
An Intel-partition starts at the value 0-1-1 and not 0-0-1
Some information here:
http://www.cgsecurity.org/wiki/Partitio ... nd_logical
Are you sure that you're running a Rebuild BS on the right partition?
Would it be possible that your partition table got changed?
Did you run a Deeper Search?
Fiona