amooz

I must apologize, I was digging through the logs on the WP server instead of my proxy server, I needed to add the following directive to actually allow the proxy:

<Location />
Order deny,allow
Allow from all
</Location>

So my new config looks like this:

NameVirtualHost *:80
NameVirtualHost *:443

<VirtualHost *:80>
        ServerName SERVER_URL
        ProxyPreserveHost On
        ProxyPass / http://1.2.3.4/
        ProxyPassReverse / http://1.2.3.4/
<Location />
Order deny,allow
Allow from all
</Location>
</VirtualHost>