Error in starting PostgreSQL Server 7.4 after crash

It all started like this:
My postgresql 7.4 running in CentOS crashed with one database missing in all my backups. But, I have a copy of the entire pgsql/data directory (which is unforunately a version grabbed while the server was still running...)

I need to recover that database and I have tried the following:

Installed postgre 7.4 again and replaced the new data folder with the one from my backup, didn't work: postgresql service couldn't start.

So, I used pg_resetxlog PGDATA with PGDATA pointing to my current /pgsql/data. It said transaction log reset. At this point, the postgresql is not running, so I cannot dump my old data. Starting the postgresql doesn't work.

So I tried: export PGDATA=/var/lib/pgsql/data
Then I tried to pg_ctl start but ended up with following message:

-bash-3.00$ pg_ctl start
FATAL: database files are incompatible with server
DETAIL: The database cluster was initialized with BLCKSZ 6330300, but the server was compiled with BLCKSZ 8192.
HINT: It looks like you need to recompile or initdb.
postmaster successfully started
-bash-3.00$

Any suggestions? Thanks in advance.

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