Mikes Carburetor parts has a 4300 rebuild kit. https://www.carburetor-parts.com/4300-rebuildkit-k7161 Note there are slight differences otf the 4300 carbs between the years so not all of the parts in Mikes rebuild kit will be used.

I highly recommend that you also install Mike's Motorcraft 4300 Secondary plug 75-45 during the rebuild

Here are my notes on rebuilding a 4300 C7DF AH on my 67 Cougar. 

Autolite 4300

1. remove air cleaner wingnut
2. disconnect oil tube at front of air cleaner and large hose at the rear of the air cleaner to the thermactor valve
3. disconnect hot air choke tube - 1/2" and 9/16" wrench
4. remove fuel line - pliers
5. remove the 3 vacuum tubes, one at front of carb going to distributor vacuum advance, PCV line at carb adapter base, and air tube at top rear of carb
6. disconnect throttle linkage at the carb
7. remove the 4 nuts at the carb base. 7/16 " socket with extension and the driver front nut with a 7/16 wrench
8. carefully lift the carb straight off the carb adapter plate as the carb will be full of gas. Don't dump the gas just yet, we will use it to judge where the fuel bowl currently sit.
9. place 4 bolts with nuts on the base of the carb to use as a carb stand Place the manifold nuts on the top side of the bolts
10. disconnect the accelerator pump arm linkage and remove the accelerator pump e-clip. I turned the clip so that the open tangs of the clip are facing up. Next use a blunt flat blade screwdriver ( mine was a screw driver that I broke the blade on so it is to thick to fit on a screw) and push down on the clip to disengage the clip from the rod. I tried putting a locking forceps on the back of the clip, sometimes it worked and other times it didn't. 
11. On the choke side, remove the e-clip at the choke plate and the e-clip at the choke rod connector. Rotate the choke up to get at the bottom e-clip
12. remove the air horn choke seal and remove the choke rod
13. remove the air cleaner stud - 3/8" wrench
14. loosen the

"I have always had trouble understanding this statement.  With the "one wire" you are sensing the alternator output which is connected to the battery with a heavy-gauge wire (very low ohms per foot).  With the 3-wire, you are sensing battery voltage through a separate, smaller-gauge wire with maybe twice as many ohms per foot as the heavier gauge wire going directly to the battery.

So for all intents and purposes, it seems to me that there isn't really any difference between the two alternator "sensing" configurations, other than one being much simpler and requiring fewer wires than the other."

There is a huge difference in sensing the battery voltage directly from the battery in a one wire system and that of a three wire system because the three wire system senses voltage NOT
directly at the battery but in stock form, it senses the voltage at the main junction splice which ties into not just the battery (source) but the accessories (sinks) as well. The three wire system will be able to adjust the alternator output based on the electrical load put on the system. Remember, your alternator should be outputting between 13.7 volts up to 14.3 volts (depending on load) whereas a fully charged battery registers roughly 12.6 volts. 

For a highly modified system (ie: trunk mounted batteries, fuel injection, aftermarket ignition systems, electrical fans, electric fuel pumps etc ...) it is imperative that you place the voltage sensing wire so that the load is properly factored into the charging solution. 

Coach Jack

 

Jerry,

On my 67 Cougar, the extra blades on the side of the ignition switch are "prove out circuits" which provides a ground for the brake warning light when the ignition is turned to the Start mode. 

Proof Circuit - Switch Position between ON and START. At a point past the ON position and before the Start position there is continuity between the proof terminal and ground P and G (via the switch body). This continuity between P and G continuity is maintained through the START position and no continuity when returned to the Run position.  

 Coach Jack

The switch has the following contacts
1. A - Accessory this is the stud mount in the center of the switch
2. B - Battery
3. I - Ignition
4. S - Start Terminal 
5. P - Proof, note on the outside of the switch itself
6. G - Ground, this is the switch body itself

Switch Position    Continuity exists only between
---------------    -------------------------------
Accesory           B and A
Off                No continuity between any two terminals
On                 B and I, B and A, A and I
Start              B and S, B and I, S and I, P and G
Proof              P and G, B and I

Proof Circuit - Switch Position between ON and START. At a point past the ON position and before the Start position there is continuity between the proof terminal and ground P and G (via the switch body). This continuity between P and G continuity is maintained through the START position and no continuity when returned to the Run position. 

Coach Jack