warm/hot backup of Postgresql

Hi,

I've been tasked with the problem of creating hot/warm backup server
of a live Postgresql server.  The problem is two-fold: 1) it's version
7.4.9 and an upgrade is not feasible at this time and b) there are
multiple instances of postgresql running on the box; not multiple
databases, multiple *servers*, each listening on a different port (it
was a business requirement from what I've been told).

I plan on using heartbeat and mon to monitor the primary server for
non-availability and fail over.

I thought about DRBD, but that would require repartitioning the live
server and I want to touch it as little as possible.

I've read the docs for WAL and the 8.2 version sounds perfect for what
I want but, as I said, an upgrade is out of the question for now.  I
see that 7.4 has WAL, but I didn't see mention of the warm backups as
mentioned in the 8.2 docs.  Can 7.4 do the same magic as 8.2 wrt to
WAL?

Is SLONY/replication my only choice?  Remember, I can't/don't want to
rebuild the existing servers.

TIA!

--

Faber