The other "early" C-4 difference is that some, referred to as the "green dot" C-4, had to be pulled into the equivalent of "2" on a modern tranny to be able to take off in 1st gear. Otherwise if you were to pull an early C-4 into "D", you would take off in 2nd gear. As I understand it this was a wet weather thing to keep you from spinning the tires when you took off on wet groung since the 1st gear was so low. My car had this set up until I replaced the old C-4 with a TCI C-4. Now it is 3,2,1 in order instead of 2,3,1
In any case if you want to keep the car as is have it rebuilt. A C-4 rebuild kit can be had for around $100. It is less than a day to rebuild if you have the tools. I've never done it, but I hear you can follow the Ford manul and easily rebuild one. Just seeing my old one sitting there, it is a very small tranny.