I have a IIS installed server and I installed SVN on the same server. I noticed that IIS occupied port 80. I change the port of the SVN service to 81. I just wondered if it's acceptable to change to the Port or if there would be consequences.
Will it work? Yes, most likely.
There is a convention, though, that if you do not want to run a service on its "assigned" port, that you instead run it on a high port, above 1024. Web services like this are frequently run on 8000, 8080, etc.