I just removed the rear end out of our mustang, Oct 64 build date San Jose V-8 single exhaust, to restore it. The rear end still had the original id tag on it. The PO had removed the vent hose fitting and used a bolt with a hole drilled in it to hold the brake line and vent the rear diff
After reading this thread on the vent hose fitting and seeing the pictures I thought I would share a picture of what I found when I looked under our car for the hose routing. There was a portion of the original hose in the clamp, the top hole was used to install the clamp, that was routed into the grommet.
I am going to clean off all the undercoating that the PO sprayed the clamp, bolt & grommet so it will have the original finish & look. I have found a used original vent fitting in great shape as well a NOS kit vent hose kit (hose has the yellow dab of paint on it). The previous PO installed air shocks on the car back around 1992 . I plan to find some more original looking type shocks and getting rid of those air shocks.