My original Pantera fronts are .763, on the caliper. The '65 Mustang are .768.
So the application that you are looking for is 65-67 Mustang.
Aftermarket like the Brembo would be an alternative.
However, I discovered that the front hub of a Mustang fits the spindle of a Pantera.
If I remember correctly, the bearings are the same?
That means that it is more then possible that the 65 Mustang with the integral hub would fit.
Of course you would need to change the studs that they come with, 1/2"-20 to metric OR change the lug nuts to the SAE size.
I don't know of anyone who has investigated this yet.
Personally I went another way. I put the "Big Ford" calipers and rotors on the front. 12" x 1.25" vented. It just required a fairly simple adapter plate.
That setup is still run in vintage Trans-am today and the Porterfield pads for it are one of the most commonly sold pads.
There is some weight gain but that is largely in the rotor itself. The difference in the weight of the calipers isn't significant at all.
The advantage here is they are "off the shelf non-exotics" and they work with your stock master.
IF you are going to mess around in the back, it would be a better then a good idea to go to a rotor to mount over the outside of the wheel flange so you don't have to mess with disassembling the entire hub assembly every time you want to resurface the rotors.
You ARE NOT going to find anyone who can cut the rears on the car.
You can find (or have made) aftermarket vented rotors built to the right offset, od, and thickness. The issue is going to be that the od of the wheel flange on the Pantera is a little larger then usual.
It's around 5.875"od. MOST of the hubs with a 4.5" wheel stud bolt circle are going to want to stay at around 5.25" to 5.375".
The simplest thing to do IF you wanted to go that route would be to cut the Pantera's wheel flanges down BUT those things are on the thin side AND the heads of the wheel studs that are used would need to be cut down as well.
SO there really isn't a simple off the shelf solution to the back brakes.
OH! Why should you worry about having to resurface the rear rotors?
Not that YOU necessarily are going to run as Komakazi hard as the Vintage Trans Am racers are, BUT if you do or intend to do "track days", you simply are not going to get the life out of the pads and the rotors as you would even just running hard on the street.
I'VE SEEN VTA cars go through three sets of pads AND rotors IN PRACTICE before the race. That may not be you but it should be a strong suggestion that maybe you should make the brakes as easy and inexpensive to change as possible? Just sayin'. 
