2 versions of Postgres on the same machine

Hi

   This is probably more like linux question but strictly related to
PG so I hope somebody can help me.

   I need to have 8.3 & 8.4 installed on the same machine (for
pg_migrator). As I'm not Linux guru I used to install/update Postgres
using yum from PGDG.

   Is there any clever way to install parallel version of PG using yum
or other way (without compilation please :D )