You can't make a rifle into a pistol. The best thing to do is wait for this:
http://www.rossiusa.com/2011newcatalog/?catalog_page=12
With a rifle, the only thing you can do is make an SBR or build something resembling a pistol with a
long barrel.
There's nothing you can do through paperwork or reserialing.
If stripped receivers were available from the factory, it would be easy. But they aren't.