The only way to do this is in the conf file.
You'll have to find the entry there. Keep in mind however that if you need support from Apple on this point, they'll tell you that you've broken the system and need to re-install. They will not help you change the conf file back. So make sure that you back up the original file BEFORE you change anything there.
The file is:
/etc/apache2/sites/0000_any_80_.conf.default
On line 4 (on mine) it reads:
<VirtualHost *:80 >
Change to:
<VirtualHost *.8080 >
There's a space between the 8080 and the >
You'll want to copy and paste the change I think. This solution will only work on the one site. If you have more than one site served from the apache server, then you need to change it system wide.
For instance... on port 8080, you'd have to change the /etc/apache2/httpd.conf file like so:
pico /etc/apache2/httpd.conf
Find the string of text: "Listen 80"
Change it to "Listen 8080"
Note that all the sites on your apache server will listen on that port.
Changing the first file will only change the one site.