Yes can 100% back up what his said there are four numbers stamped by the dizzy, Cosworth asked for only grades 2 and 3 (Bore tolerances as explained above) to be delivered to them, once you rebore these numbers become totally irrelevant anyway.

The only other difference being is that 'Cosworth' blocks have YB then a four digit number stamped on the front, that and the above aside there is no difference.

Whoever told you such have told you wrong and obviously don't know what there talking about

There is however a 200 block which was fitted to the 4x4/Escos this was stronger and also the YBD (RS500 had a stonger block named 205, this is NOT the same as a Pinto block)

Now the trivia, 20 means 2 litres displacement and the 5 was appened from 1985 when the block was revised before this the blocks were simply called 20.

Martin