66 fender tag decode, think I have a clone

A clone to what? What do you think you have?

I posted this then saw your other thread. You have a 66 Barracuda that came with a 273 2bbl. from the factory. It is quite common for people to add the 4 bbl and Commando valve covers and air cleaner. It was also common for people to add this stuff new from the dealer. Either way drive it and enjoy it. These care are not a gold mine when it comes to resale and collector status, but they are also affordable for the average Joe.