The ammeter wiring goes through the choke cable hole for early cars. For later 350's there is an added hole for the wiring.
as Dave said, above. Since GT500's had electric automatic choke all the GT500's used the Ford choke hole for the oil line and Amp gauge wire - no extra hole added.
(Edit thanks Bob!)
In JDs pic:

the early car has what appears to be a 65-66 choke cable grommet (sold at Virginia Mustang) while the later car has what my breakdown shows as a 379150-S rubber plug in the upper location.
Interestingly, an old pic of my car appears to show the early choke cable grommet at the bottom. The pic isn't very clear and the grommet appears to be broken in half.
I've included a zoomed in pic of the area showing the beveled plug at the top and a shadow of what looks like half of a 65-66 plug below.
[the car had a/c retrofitted, hence the plate gooped in when it was later removed.
Also bungies and wires are holding up the trans].
I'm not sure if I should use the beveled plug in both places (like JD's pic) or put back what I found. No telling what's stock in the chock cable hole due to the a/c stuff.