Hi!
Generally, it is more work to upgrade the older the version is. 1339 is almost 2 years old.
Could you explain in more detail how it doesn't work? Usually, it is just a matter of adding the correct references and removing old stuff from web.config to make it work.
If you think it will be easier to upgrade to 1504, you can find the GUIDs for all Webnodes builds here: http://services.webnodes.com/license/?action=builds&kode=1234
Vidar