You find that It isn't in EPEL, and it isn't in Red Hat Optional Server 6 RHN channel, etc.
Note that mod_proxy_ajp is a core module of Apache 2.2 and newer so this should be a rather definitive/final change in recommended connector for Tomcat and Apache.
Read the docs, but to get you started in configuration first you'll want to configure Tomcat's conf/server.xml file to have something like (which may already exist):
<Connector port="8009" enableLookups="false" redirectPort="8443" protocol="AJP/1.3" />
And Apache with something like:
<Proxy *> AddDefaultCharset Off Order deny,allow Allow from all </Proxy> ProxyPass / ajp://localhost:8009/ ProxyPassReverse / ajp://localhost:8009/