I want to reconfigure a Synology running latest DSM 5 to work on normal HTTP ports.
The default configuration is to use port 5000 and 5001 for HTTPS and I do not like these because they are quite often blocked by most firewalls (in addition to the accessibility and visual aspects)
You can change this in your DSM Control Panel. Under Connectivity > Network > DSM Settings you can set the ports.
Obviously, make sure that if you have another webserver running on your NAS like Apache, it doesn't listen on those ports.