The recent ebay one was actually a C4ZF. Quite rare, believe it went for over $500.
Keep in mind the biggest difference between the C8 units and the earlier pieces is the outlet pipe, which would be 5/16" diameter on early cars and 3/8" later on.
Agree with Phill that I would choose a C8 over any reproduction. John's Mustang in Texas had them in their catalog recently.