Not sure I fully understand the total context of this from your explanation.
From what I can understand, you want end users to retrieve FSA archived data from a web browser using specific ports.
If that is the case, you can access FSA archived items via Archiveexplorer which is a structured view of the archive in a split pane web browser format. From the end user point of view this is purelly HTTP/HTTPS. So you should have no need to configure any 'customer' specified ports. As long as you can contact the EV webapp from the client through the firewall, there is nothing else to be configured. All the hard work is done between whatever File Server Storage you have and the EV App.
As a simplistic flow diargram, End user call via HTTP/HTTPS to EVWebapp via Firewall. No need for translation as it is a HTTP call to the EV Webapp, and 80/443 should be enabled by default. EV will then do the back end work and deliver the archived item back to the End user via HTTP/HTTPS.
The only caveat to that is that you may need to publish an Alias for the EVServer on the dirty side of your firewall, this i am not 100% sure on. look at guides setting up RPC over HTTP. Heres a start
http://www.symantec.com/docs/HOWTO38205
