The only way to do it in 5.3 is to right click on each asset and choose "duplicate" which allows you to specify a different project.
Though its not easy... I have used TP to automate TP for things like this before. Its not easy because you have to use Identify, hand write the script, and run the script back from a command line.
I think you know that duplicating a project in 5.4 is very simple using import/export. The only note is that after you export you have to change the project name attribute in the XML to the name of the (new) project you want to move the assets to.