It's become standard practice to consider the 65-73 the same generation, maybe because they were similar under the skin and the Mustang II ensured everyone thinks of the II as the second generation Mustang???
Sold my 66 GT350 mustang rapidly, glad I did! The Mustang E is a stinky stain to every Mustang that came before it! The marketing department at Ford is lost in my opinion, especially since they had the name Thunderbird at their opportunity.