Hi Roque,
do you overload a server if you install both applicationsin one server? oohh that is a heavy weight one!
If it is not possible or wanted to run the application within the same cluster you might try the autodiscovery feature.
Set only the correct autodiscovery address within the JNDI lookup (autodiscovery is enabled by default).
Remember that network multicasting must be enabled between the two JBoss installations, network switches often drop this packages!
In this case the other JBoss(es) will be found by network broadcast you only have to configure autodiscovery correct.
But I still suppose there is a chance to run both applications within one server and build a cluster of JBoss instances to handle the load.