I wish to use the Helvetica package. I installed the psnfss package with tlmgr (and in a fit of desperation other font-related packages, such as times and ae). However, I still do not have any phvr7t files in my texlive distribution. I do have phvr8g.tfm, phvro8g.tfm, phvr8gn.tfm and phvro8gn.tfm at /texmf-dist/fonts/tfm/metapost/, if that helps.
I used the Mactex texlive-2012-basic installer.
EDIT: I manually installed psnfss, because tlmgr did not copy any font files into the texmf distro. I now have phvr7t.tfm and phvr7t.vf at /texmf/fonts, but Latex can't seem to find them.

tlmgr: which is it? – Joseph Wright♦ Aug 15 '12 at 15:16