Somebody put a '66 Sprint air cleaner on your '65. It's been over 50 years now so a lot of things could have been changed by POs.

 

Or a sprint sticker on a regular air cleaner. A sprint would be chrome. Also, there’s a decent chance that that whole engine is from a 66. Should be a black block with red valve cover and air cleaner for 65.

 

The Sprint was Ford's way of celebrating the millionth Mustang, which wasn't yet built in 1965.

 

My 66#1 was a sprint. It's been years since I had it, but as I recall, it didn't have an open air cleaner. It was like a chrome dog dish.

I agree with the others: you have a '66 sticker on an otherwise '65.