problems to restore database with custom datatypes (e.g. txtidx)

Hi,

I have two datatbases running postgres 7.2. The production
database is replicated to the backup datatbase once a night
using pg_dumpall -g ... | psql -h backup
and pg_dump -c ... | psql -h backup

This worked fine until I installed txtidx from
contrib/tsearch.

The install-sql-file from tsearch installs some functions
which would get replicated like any others. The same
seems to be true for operators and types.
Nevertheless the replicated database cant use the datatype
nor the corresponding index type.

The install scripts modified some system tables so I replicated
much of it by hand but now, although able to create the
table with the column, I cant recreate the index.
I further fear that dropping the functions during the replication
changes their oids again and the type would not work anymore.

The failure from creating the index is:

fmgr_info: function 0: cache lookup failed

I could run some functions to clean up the database after copy and
reconnect the functions like I did by hand, but I have to flush
the function cache as it seems.

What can I do? Are there solutions to mirror the system tables too?
Or even make a real mirror where the very same oids are used?

Regards
Tino