Earliest 340 production date/number

Saw a picture of the side of a guy's 340 on another site, thought it looked very close, if not the same date, as my older 340 (I have two, the younger one is from '69). Went and snapped a shot to show him- mine is two months earlier exactly. His is 8/22/67, mine is 6/22/67

Both are pretty early in the 340 production. Any ideas of when 340 production actually started?

And, yes, I am going to stuff this motor in a car. I have an '85 AHB Plymouth cop car that would be loads more fun with a warmed-over 340 in it as opposed to a smogger 318, 4-bbl.(which weirdly has a "Premium Recommended" sticker on the inside of the fuel door).