Not sure I’m following the 4150 & 4160 references Bob, these two-barrel carbs are known as 2300 series Holleys, some similar attributes like metering plates. The original 4144 & 4374 California only center carbs used the same bowl as ’71, with the enclosed idle bowl vent valve. Agree, that date “1” date code year, not likely to be an original 4144 ’70 production carb. Besides the later Holley aftermarket, could also have been purchased as a standard Chrysler replacement part back then, using the original Chrysler part number. I was buying these through the normal dealer parts channels well into the late seventies from the dealer I work for then, pretty cheap too I might add. They were also offered through Direct Connection later, Mopar Performance, up until the mid 2000s using a later “P” part number. The “1” date code year could be ’81,’91, or even ’01. The re-issues were list 4144 for the ’69-70 applications and list 4670 for ’71, later eventually dropping the 4144 re-issue altogether.
The mentioned change to hex-head float bowl screw started with the re-issues much later, there were some other slight hardware/fastener changes as well.