Hi Natedawg,
Is the hole too small, or too big, on the back of the engine? Can you measure the pilot hole? I looked up on Rock auto a torque converter for a 75 pinto C3, and it is the same for a 80 C3. They do however call it a stepped pilot, 0.875" to 0.750". I do not remember but i think the converter I sold you is only the 0.75" pilot. Please let me know the details, and if the converter doesn't work out, you can keep it and I will give you some money back.
Dennis