I can't find those packages in synaptic.
Would this driver be in these packages? :
You said that you installed 64 bit RC1. That comes with the nvidia304 packages pre-installed. Unless you removed them they should be present.
Failing that, in order to install them you will need to enable the "test" section in Synaptic (the packages are not in the stable section yet).
Go into Synaptic->Settings->Repositories
Select your mirror
Add the word "test" to the sections
OK and do a "Reload"
Then search on nvidia304
Remember to disable "test" afterwards (before doing a full update)