Um ... I hope you have a lot of time on your hands. It will likely take a few months to work out a functional installation using that route.
Note that Vicidial is a PBX. Installing it ON a PBX is redundant and very likely to result in chaos/conflicts.
It is NOT recommended to "combine" the Vicidial server with any other server. It will likely take a huge number of man-hours (unless you are already good at installation of this software and know all the ins and outs, such as Kumba, Gardo, or PoundTeam) and when you are finished ... you have forked the project and are not likely to benefit from upgrades or bug fixes. Which means that in six months, you'll be tempted to do it again. Vicidial servers are also clusterable (many servers, many users wandering between them). When your system outgrows your single server solution ... you'll want to add new servers.
Also, Vicidial is HD intense. It kills hard drives (thus the enterprise versions with RAID10 on SSDs!). And once you have several in operation, any one of them can die a horrible HD screaming death at any given moment in time. Ordinarily, this is just "bummer, server 3 is down, have all those guys log out and back in and build a new one". When the rebuild is done (can be done in under an hour, and even less time if you have a "hot spare" ready for new IP and configuration file values), new agents will suddenly (automatically) log into server 3 again (the new one) and likely not even know (or care).
Whereas if you install Vicibox.com's stock .iso image, you could be up in about 30 minutes and you could upgrade at will and you could integrate with any software on any other linux-based system on the planet (ok, linux isn't a requirement, actually ANY system with internet, LOL). And adding new servers to the cluster is built in to the .iso (thanks Kumba!!). Death of a server is cause for "concern", but not panic. (Server three is dead ..., wait for it ..., Long Live Server three!)
Note that Vicidial is NOT "just a web site". It's not Wordpress. LOL It is a combination of a web server, a mysql database server, a PBX server (running a specially patched version of asterisk), and an application server running 7-12 services in "screens" in addition to the fact that php/javascript/html/AJAX are all heavily used on the web server and PERL/php are heavily used in other systems. Versions of all these make a difference, and interaction of various versions makes a difference as well.
That being said, it's not impossible to do ... just not really a great idea. A better solution is probably available to accomplish your task to the client requirements, likely with much more hair on your head at the end of the run (and a lot more money still in the client's pocket). For instance, if you want just some of the web services to be run from a random web server, that'll work. But "dialer" and "agent web" can be a bit of a challenge. And require some power.
So ... WHY do they want you to put Vicidial on THAT .iso?
(NOTE: Vicidial is A not compatible with any asterisk version after 1.8 and B versions after 1.8 are not stable, they segfault ... which is both your problem today and why Vicidial is not yet compatible with versions after 1.8! LOL)