Just a Heads up, the 73 Mustang electric choke for the oem carburetor was fed by Circuit #4 (White with Black Stripe), which is fed by the alternator stator terminal. The electrical output from the stator terminal on the alternator provides current that is not like any other circuits' current in the vehicle. The stator output is AC, not DC current, and it is half the voltage of the alternator output that is sent to the battery.
If your Mustang is a 73, although the oem choke heater circuit will "connect" to the aftermarket electric choke, the aftermarket carburetors with electric choke requires 12 volts of voltage to operate as designed. Using the stator circuit may eventually open the choke, but it is best to bring it full better voltage.
For 1973 there are a few ways to get 12 volts of switched power pretty easily. And I have used both for various projects in the pastmcouple of years.I prefer to use the current from the Throttle Position Solenoid, or the Red wire feeding the windshield wiper motor. Once a great while I have used a relay, where the trigger voltage (which causes the relay to close the load related circuit) cab come from several places. Using a relay for the electric chike =may be a little over the top, but such a design would work if you find it viable for your situation.
Of course, I have a video that shows how to use switched 12 volts to power an aftermarket carburetor electric chok. The prior owner of our 73 Mach 1 had its electric choke wired incorrectly, where the Starter Relay's "I" (Ignition) terminal sent voltage that was too low to the electric choke cap. No wonder the engine ran so rich when cold, and fuel fouled the spark plugs! The video shows how I required the current feeding the electric choke. This may prove to be useful to you. The link for the video Lynda and I put together is at the following web site:
https://youtu.be/WDcskIPfLcE