year of /6

I need to find if the /6 in my 65 barracuda is original. I bought a cylinder head gasket set and everthing was ok. I ordered a valve cover gasket from the same place and is is totally wrong. I looked up the part numbers and it shows to be correct unless Felpro put the wrong part in the box. It had to be ordered so I'll have to order again.
As always, thanks for your help
Tommy