Well, the only rpm repository out there offering subversion above 1.4.x was / is rpmforge (aka DAG).
In order to add rpmforge to your RedHat / CentOs repository one has to update their yum repositories by installing the rpmforge-release package which you can also find @: http://packages.sw.be/rpmforge-release/
The problem I encountered was, I had a Centos 5.5 x86_64 with subversion & mod_dav_svn 1.4.2, after updating to the latest rpmforge-release, I expected a