Installing to drive in USB enclosure?

[Andrew Moise]

  So I'm installing a new drive in a computer (vino).  The new drive is
installed in a USB enclosure attached to my old computer (mole).  I've
copied all the files over to it, and now I just need to install grub on
it.  Is there any way to do this?  I don't see any way in the grub
documentation, and nobody could help me in IRC.  This seems like a
pretty common use case.
  I have grub installed on vino currently, so I can copy any information
over (or even dd disk sectors around) if need be.
  I'm running GNU/Linux, and the drive in the USB enclosure appears as
/dev/sda on mole.