Identify heads ?

You won't be able to tell for sure unless you pull the heads and look along the underside for the casting numbers. Later model heads will have thermactor bumps in the exhaust ports, but that still won't tell you which late model head you've got. If I remember correctly, the E7TE heads used on the mustang have the letter "T" stamped in the oil galley located under either valve cover (which stood for truck, as this is where they heads were pirated from), but otherwise, pulling them is your only option.