http://wiki.vicidial.org/index.php/SVN:howtohas a lot of info including a link at the end to another forum topic with a description.
When we do this, we use "svn info" on the "target machine" (the machine with the version we want to "match"), and then "svn up -r 1559" (with the appropriate matching revision number) in the trunk folder on the machine to be upgraded.
After this, you execute "perl install.pl" in the trunk folder and answer the questions, and then learn how to "cluster" this box into the other one (google poundteam multi-server manual for this part). To be clear, this install package will copy all the necessary files to their locations, that's it's job. DO say "Yes" to the sample .conf files question.
A MUCH better solution would be to upgrade your existing system to the latest SVN and then install a brand new server with Vicibox 4.0 which will do all the clustering for you (and add itself to the cluster!). Then you get the best of both worlds: Clustered and all the new toys ... and the PoundTeam Multi-Server Manual is merely a reference for stuff Vicibox already did for you (ie: redundant).