The 4 numbers you are referring to are stamped on the block by the dissi after production and are the bore tolerances of each cylinder - they are nothing to do with the material the block is made from.

All the Pinto 205 blocks were stamped depending on how close to the correct bore each cylinder is, these vary depending on how accurate the boring machines are set up on the production line.

number "2" represents the closest to Factory tolerance a bored cylinder can be, therefore all the blocks that had 4 bores all with number "2" were selected, and put to one side for the cosworth engines thats why you will see on a cosworth block 2222 under the dissi, the rest went onto normal 2 litre sierra builds

those with numbers either side of 2 ie 1, 3 4 are either slightly undersize or slightly oversize - they still accept standard pistons but are not the optimum size - the undersized bores can be brought up to "2" by simply honing the bore, they dont need re-boring

Very few of the 202 block that were kicking around were "2222" some were over some under some blocks had under and over the optimum.