Default Operator Class for datatype

Hello,

I've set pl_PL.UTF-8 collation on my database after upgrade do 9.0.
That means indexes for varchar column doesn't work anymore in selects
using "like" or "=" operators with that columns.
I know the solution - operator classes - which works very well.
But that means I have to find and recreate all indexes on varchar
column like this:
CREATE INDEX test_index ON test_table (col varchar_pattern_ops);

Does anybody know if there is any possibility to set a default
operator class for varchar datatatype?
I can see that in system table pg_catalog.pg_opclass ther is a column
called "opcdefault". Does anybody has an experience with changing that
value? The idea is to set this default operator class and make after
that dump-restore of database data. Should work.

Best regards,

Jakub