340 ID help please

right the 71 spec blue engines were still 2.02's and 10.2to 1, but any 72 duster /demon cuda etc.. was low perf compared to the 71 and earlier. So the OP 6/71 block was most certainly a blue engine because it was cast two months after 340's were leaving the showroom floors with blue engines , i also have a 1/22/71 340 warranty block that is blue but not sure of the build date