John,
I have a spreadsheet on materials, finishes, paint daubs, and grease pencil inspection marks for C3OF-AB, C3OF-AJ 1963 and 1964 (one engineering number but some small changes were made for 1964), and C4OF-AL carburetors used as O.E. on HP289 powered Cobras. It has taken decades to collect all this trivia. Buying new old stock production and new car take off carburetors as samples helped a lot. Details of a few less than 10,000 miles from new Cobras added to the database or confirmed what I already had. If I was doing a HP260 carburetor I would detail it like a C3OF-AB unit as they are very similar in all ways. C4OF-AT assemblies used with automatic transmission Cobras were built in April 1964 along side C4OF-AL assemblies so I would use the suffix AL information for the suffix AT assemblies. (I did when I cleaned up and serviced a unit for CSX2580 earlier this year. The air cleaner stud is a nos one but all the other parts were just carefully cleaned except the secondary throttle shaft, which needed some repair work.)
I also have many close up color pictures I took long long ago of a new old stock C3OF-AJ carburetor dated 3EE.
Want a spreadsheet copy emailed?