One of my favorite commands on SPLAT is webui. It allows you to set WEbUI on a custom port, if you like. For example, to set it on port 4434 you just need to run the following: webui enable 4434
But be careful, with R75 and up the behavior has been changed. Even if you set it up on a custom port as described above, it will get back to default 443 after reboot.
This is quite annoying, especially if you have Mobile Access Blade with SSL portal running on your GW. But no worries, there is another place, rather unusual, where you can set it up right.
For your R75 and R75.X objects, go to SmartDashboard, then double click to the managed object and choose SecurePlatform tab.
In the "Main URL" field add your port, as shown on the picture above. Push policy, now it is all good.