I have an A-75-8 on my Champ and I do know the difference between the A-65 and an A-75. I helped my IA in converting the engine some years ago. The only differences are some internal parts changes, like drilled rods, different carb parts, prop dia. and pitch change, remarking the tach from 2300 to a 2600RPM red line, and a new data plate from Continental.
All this is covered in the Continental Service Bulletin M47-16.
I was unsure if there was a C-75 designation in addition to the A-75, and yes, you are correct, there is.
But, I still stand by my statement that there is NO such thing as a C-65 Continental engine as designated by the factory, even though some people mistakenly call it that.
An A-65-8 has no place on the rear accessory case machined for accepting a starter or generator, the -12 has those pads built in for those parts. So, whether it has an electrical system or not is defined by the -8 or -12 after the 65, or 75 HP designation, NOT by the A or C in the front.
A properly adjusted cable operated drum or disc brake system does not require a large stopping distance. Mine are just fine with drums, in fact you do not want too much stopping power, like with hydraulic discs. It's too easy to put the plane up on it's nose with poor use of the brakes. Hydraulic brakes are just not needed or wanted on such a light plane.