Systems Management

Hello I have a question about creating packages that are able to be customized for each site. I will give an example below, but first just a little background.
I work for a very large company (~75,000 users) and we are switching from a really bad software distribution system to SCCM. Previously we hacked together a solution for dealing with local site customizations to packages and I would just like to figure out a better way.

Example:
We have a Symantec Ghost client package that we deploy, the actual install is the same for each site but the server it connects to is different. We need a way to install the same package but provide a different server depending on what site it is being installed at. With our previous tool we had local site administrators create .ini files that pointed to the correct server and then scripted into our package to look for this INI file.

We can't create a separate package for each site, because we have 106 sites. Does anyone have any ideas?

Any help is appreciated!