Also......

Warranty blocks had warranty tags riveted to the side of the block.

T/A blocks were also sold to anyone that wanted to buy one.

Neither type had a stamped VIN.

The T/As & AARs I have seen so far with actual blocks replaced under warranty have regular 340 blocks.

They would just send out what they had to fix the issue, there was no guarantee that a T/A block would be sent.