You can tell what version an injected head is by looking at the middle cylinder head bolt area on the manifold side (the bolts that are not inside the valve cover.
Basically, there are E heads, early F heads, and late F heads.
That middle cylinder head bolts sits on a little raised area of metal, machined flat with the rest of the top surface of the head.
If the bolt is in an isolated 'island' of raised machined metal, surrounded by lower rough cast metal, it's a E head.
If the bolt surface is connected on one side with a thin raised 'isthmus' of metal to one of the nearby bolt heads, it's an early F head.
If it is connected on two sides to both bolts it's a late F head.
There's very little difference in the heads in stock form other than the E head's lower surface is machined down a lot more to make the combustion chambers, and compression ratio higher. In stock form, both F heads were thicker and had lower CR's, but they can (and sometimes have been) shaved down considerably to raise the CR after 50 years of being tinkered with. Apparently, the late F heads have extra metal around the exhaust ports and in the right hands can worked more for better flow. Without any porting work, there's not much of a difference.