Recover original superblock on corrupted filesystem?

[bloch at verdurin.com]

I've been trying to use fsck to recover a corrupted filesystem.

It appears the original superblock is corrupted too, as it has an inode
count of 0.  When I start fsck with -b 32760, it uses the alternate
superblock and proceeds.  However, it restarts from the beginning a
couple of times and after the second restart it doesn't use the
alternate superblock, stopping instead as it can't find the original
one.

Is there a way around this, such as using one of the alternate
superblocks to replace the broken one, or a way of forcing fsck to keep
on using the alternate one?  The checking process is taking several
hours in each case, as it's quite a large filesystem.

Thanks for any suggestions.

Adam