[Koha] non-standard classification source

We've been using a proprietary classification source and would like for Shelf and Call number to reflect our system in the OPAC. How do we do this? I'd like to enter our shelving options in a Zebra table and then allow the cataloguer to choose from a drop-down list in the Items step, no? Secondly, several libraries are involved and some of them do use Dewey. Is a single installation able to handle multiple classification sources? Thanks, Nelson Fredsell Cape Town, South Africa