Earliest 340 production date/number

Rob R said
The earliest for me was a 2-67 and it had a couple of things that I've never seen before..it had a serial number on the drivers front of the block 00007 and it had one machined pocket on both deck surfaces that told you the deck height when you dropped a dial gauge into it..

Now that is early.... Never seen one cast that early. Would stand to reason. 68 model cars were probably released around june or so of 67? usually blocks were cast 2-3 mo. before vehicle production date, maybe sooner being a brand new engine at the time