PCV was standard equipment everywhere starting in '63 ('62 in NY; '61 in CA).
There is no "correct" 2bbl intake manifold for a '65 Slant-6; the first factory 2bbl setup on the Slant-6—not available in the US or Canada—started in '67. Not til '77 in upper North America. None of the 2bbl intakes has a pass-through port on the carb mount pad for PCV; that's only on the Slant-6 1bbl carbs. The 2bbl PCV porting is via the throttle body and/or the carb base gasket + insulator.
feel certain that if I drill a matching home in the manifold that I will have vacuum at the PCV, but I'm hesitating to do that unless I have some confidence that it will address the hesitation issue.