My 67 mustang which was supposed to have the original 289 in it, doesnt. My first ford here. I ordered spark plugs for the 289 only to find out they are way to big for the spark plug holes in my car. When I changed the valve cover gaskets, I did notice it said windsor on the inside of the head. Is there anyway to find out what this motor is , easily?

 

Pretty sure the number for the block is under the starter on the bottom of the block.
Someone has a picture, I'm sure they will post it for ya. Possible someone changed out the heads on ya?