mod_cluster requires version 5.0 or later of JBoss AS.
i will use mod_jk
Actually, it might work to use mod_cluster on JBoss 4.x by configuring it as if for Tomcat - though I have not tried it. If you do, let us know how it goes.
copy the JBossWeb-Tomcat/lib/mod-cluster.jar to server/[default]/deploy/jboss-web.deployer.
Of couse it works like when used with Tomcat.