Upgrade 7.3.3 to 7.4.5

Hi,

I upgraded recently DB and found that some columns with type "timestamp"
changed default values from now() to:
receipt_date | timestamp with time zone | not null default
'2004-09-29 09:58:03.010678+10'::timestamp with time zone

,where time is a time when psql -U postgres template1 < db_backup.sql was
executed.

I want to underline not all "timestamp default now()" columns but only some
of them.

Any ideas?

Thank you,

Igor