Thanks for the post. Just for those who are also searching, here are some things to look for
STI ej207 injectors are pink which can be seen if use a torch (wrx ones are blue but obviously the sti injectors can be swapped as an upgrade)
Red inlet manifold but obviously could be painted or swapped
There is a sticker on the bottom of the left hand side timing belt cover as your looking at the engine which will say ej207 or ej205 but it is likely the sticker would be faded or gone
If you remove the timing belt covers it will have the avcs cam pulleys (variable valve timing) if it is an ej207 however I believe the later wrx engines had avcs but I am unsure. The avcs also has a solenoid on the top of the cylinder head.
The ej207 uses a closed deck / semi closed deck block which has hatch marking on the engine casing somewhere I believe but not 100% certain.
If anyone can confirm these points / update any mistakes for future reference it would be appreciated