You can try to edit the Nautilus source code to scale the font in the zoom like in Nautilus 3.4.
NOTE: In this example I'm running ubuntu 13.04 with nautilus (files) 3.6.3.
You can test this in a virtual machine to see if everything is OK.
First of all, I set the Nautilus Prefereces in "List View" as Default View and "200%" the zoom in List View Defaults.


By default the result with no scale font would be:

1) Make sure you have enable the Source code repository
- Open the Ubuntu Software Center
- In the Menu Bar choose Edit -> Software Sources. Click to enable "Source code repository".
Just in case I use the "Main Server" to Download.

Open a Terminal window and type:
2) In the Terminal type the following to install the necessary packages.
sudo apt-get install build-essential quilt
3) Install build dependencies.
sudo apt-get build-dep nautilus
4) Create a folder to download the source code.
mkdir ~/Downloads/src
cd ~/Downloads/src
5) Download the source code & Export variables.
6) Create the patch and Edit the source code.
After line 133 add:
static void nautilus_list_view_scale_font_size (NautilusListView *view,
NautilusZoomLevel new_level);

After line 2506 add:
static void
nautilus_list_view_scale_font_size (NautilusListView *view,
NautilusZoomLevel new_level)
{
GList *l;
static gboolean first_time = TRUE;
static double pango_scale[7];
int medium;
int i;
g_return_if_fail (new_level >= NAUTILUS_ZOOM_LEVEL_SMALLEST &&
new_level <= NAUTILUS_ZOOM_LEVEL_LARGEST);
if (first_time) {
first_time = FALSE;
medium = NAUTILUS_ZOOM_LEVEL_SMALLER;
pango_scale[medium] = PANGO_SCALE_MEDIUM;
for (i = medium; i > NAUTILUS_ZOOM_LEVEL_SMALLEST; i--) {
pango_scale[i - 1] = (1 / 1.2) * pango_scale[i];
}
for (i = medium; i < NAUTILUS_ZOOM_LEVEL_LARGEST; i++) {
pango_scale[i + 1] = 1.2 * pango_scale[i];
}
}
g_object_set (G_OBJECT (view->details->file_name_cell),
"scale", pango_scale[new_level],
NULL);
for (l = view->details->cells; l != NULL; l = l->next) {
g_object_set (G_OBJECT (l->data),
"scale", pango_scale[new_level],
NULL);
}
}

After line 2569 add:
/* Scale text. */
nautilus_list_view_scale_font_size (view, new_level);

Remove lines 3051 & 3052.
/* ensure that the zoom level is always set before settings up the tree view columns */
list_view->details->zoom_level = get_default_zoom_level ();

7) Build the deb packages.
quilt refresh
fakeroot dpkg-buildpackage
8) Install the deb packages.
9) Finally you can Logout and Login to see the changes.
Result:

NOTE: You can zoom in, zoom out with the Ctrl + Mouse Whell or with Ctrol++ & Ctrol+- keys.
Hope it helps.