I believe you have mis-interpreted the info from the site across the pond. It says an "AC289" does not have any side badges - the "AC289" is not a Cobra - it's a 427 style aluminum body with a 289 engine, and was built and marketed by AC Cars, NOT Shelby-American.
Original 2000 series small-block Cobras DO have a side fender badge - they look like this:
Obviously, it's not going to say "427" on it - it just says "Powered by Ford". This badge was used on all the street cars - even CSX2000 has one. These badges, along with the 2" round ones for the nose and deck, are often NOT found on factory "competition" cars.
Here is the badge for the BB cars:
The location of the badges on the front fenders is different between small-block and big-block cars, too. On small-block Cobras, the badge is located further back on the fender, close to the door cutline. On big-block cars, it is further forward, above the louvers in the side flanks of the fenders.
regards,
cobrajeff