Trying to create implicit casts to text in PG 8.3

Hi, everyone.

I'm trying to upgrade a database which is used by several hundred installations of an app; with each installation
possibly running some custom code and 3rd party extensions. I was hoping that it would be possible to re-add implicit
casts to text for bacwards compatibility with 8.2, since that would be much easier and smoother than testing all those
installations and/or waiting for bug reports to start pouring in...

I tried adding casts found here:
http://code.open-bio.org/svnweb/index.cgi/biosql/revision?rev=284

Function calls work fine now, but a new problem appeared with operators:
SELECT EXTRACT(DAY FROM NOW()) || 'abc';
ERROR: operator is not unique: double precision || unknown

Is there a way to get around this?

Regards,
Aleksander