Welcome, Alex!
It's been a day since I've had eyeballs on an AC car from that era with a 2bbl, particularly a '65.
That said, there is a fellow in Switzerland (no kidding) with what looks like pretty much a survivor car (another Star Chief, like yours) who may be able to help:
https://foreverpontiac.com/forums/to...65-star-chief/
He may be able to shed some light on your inquiry.