There are various ways to achieve this, probably depending on which ezp version you're using.
With 3.2-2, you can use the URL translator to create a forwarding URL from /content/view/full/49 to /content/view/full/63.
What you're using will work too, but it needs some editing. The "content_node" attribute of node_view_gui expects a node, not just an ID. Just fetch the node, and pass it to node_view gui.