What Car have you got?
The EJ205 was standard block for a WRX
EJ207 was the block used in a STI
They all have EJ20 written on them it's mainly the pistons and rods that vary on these i believe. I cannot recall if the EJ205 block was semi closed or not, i'm guessing it was a Open deckl block, where as the EJ207 is semiclosed for sure.
Hope this helps...