Creating 'global' functions.

Is there a way, when a function is created (in language SQL for example),
for it to be available globally, as the pg_catalog functions are. All of
the ones I create are only available on the database they were created,
and I can't figure out a way to make it so they're available to all
without having to run the functions in every database. When you run a
select on pg_proc they won't even appear, but all of the 'catalog' ones
will.

These are generic cast functions that needed to be written when we
migrated from 7.2 to 7.3, so they don't reference any specific database
tables or anything like that, but all of the databases NEED these
functions to operate the way the queries were written. I tried to change
the proowner and pronamespace in pg_proc and these didn't seem to do
anything.

I worked with this a few days with no luck at all, and just ended up
running the creation scripts in all of our databases, but it would be nice
to know if it's possible.

Thanks!