The 205 blocks were selected for there bore tolerance, Cosworth asked for only Grade 2 and 3 so if you look by the dizzy you will see 4 numbers I.E 2222 is a Cosworth block, it will also have YBB then a 4 digit number by the water pump engraved into the block apart from there there is no difference, once you rebore these numbers become totally irrelevant anyway.

Martin