or would it be better to just to make it work with 2.2.3?
CentOS 5 ships httpd 2.2.3 by default. Don't worry too much about the older version number. Apache httpd 2.2.3 with many security fixes which are back-ported by RedHat.
One good reason to stay with 2.2.3 is that it's the default package that comes with RedHat/CentOS. It's a known and stable version, the RedHat/CentOS documentation is written with 2.2.3 in mind and most other users will be using 2.2.3.
Using the defaults will also make future upgrades go better. For example, you would have been able to do a
yum upgrade mod_dav_svn today, without breaking the application.
Custom packages are fine, but it's often better if they are installed to
/usr/local so they won't collide with the default packages.
previously installed version was 2.2.16
How was this package installed? Was this a third party RPM? Or was it installed from source?
Have you checked other locations for another version of httpd, such as at