Dumping Postgresql 7.4.2 database file into Postgresql 7.1.3 or 7.3 or 7.2 databases

Hi all.
I have got a database in 7.4.2 version of  postgres ....I have taken
out the dump of it...I would like to dump it into the previous
versions of postgres mainly 7.1.3 and 7.3.2 ....but couldnt do so
because the format of dump files in these versions are different from
the 7.4.2 version...please help me out in this case ...as this is
urgent ...i want to dump my database into the previous versions.Thanks
in advance

Ravi Shankar