I am reading March 16, 1966, final assembly date March 18, 1966. It fall within what has been explained previously as "acceptable" but, IMHO, maybe a ew weeks too early. I say this because it was only 2 days from casting to finished, supply (stock/inventory) was running out fast as they could build them.
That being said, if the bore and block are in good rebuildable condition, I PERSONALLY do not see any problem with using it anyways. The date spread seems to be acceptable to those judging these cars.