Can I convince svn 1.5 that a random directory is really a branch off of trunk?

I recently used the Polarion converter to import my MKS repository to svn.
I had to make some changes to support a cutoff point based on date for the
export out of MKS. I confused the importer and now my svn repository has
branches the are really adds of 1000s of files instead of a proper branch.

Is there a way for me to tell SVN that "project/branch/1.0_integration" came
from trunk @ revision 450?

Right now, when I try to merge between branches merge the svn application
takes 100% cpu and gobbles up all of my ram before terminating with an
out-of-memory error.

I can dump my repository and rebuild it with a skeleton of tags branching
where appropriate, but I'll loose the who-did-what history and I'd really
like to keep that.

So, anyone have any ideas? Or can someone point me at the right place for
me to RTFM?

Thanks.

-- 
Peter Kahn
citizenkahn_at_gmail.com
pkahnpie1_at_AIM
http://citizenkahn.myplaxo.com
Awareness - Intention - Action